"I never thought Caesar would distrust the Vestal Virgins." Myria, the Vestalis Maxima, said with an amused smile. "Must you inspect even such trivial matters in person?"
"Because it is that important."
I gazed at the sacred flame burning brightly at the center of the temple.
Come to think of it, the Vestal Virgins had helped me when I first introduced Palmolive, too.
I never imagined I would have to ask for their aid once again like this.
"For hundreds of years, our Temple of Vesta has safeguarded the wills and public documents of the citizens. Not once has a single secret ever been leaked."
"I am well aware of that."
Roman politicians frequently entrusted their most vital wills and state documents to the Vestal Virgins.
No one was allowed to inspect them at will.
The man who would one day famously shatter this sacred tradition was Octavian.
He would seize Mark Antony's will and read it aloud before the Senate.
It was an unprecedented act, widely condemned as sacrilege.
"However, I understand that the priestesses are free to retire once they complete their term of service—and to marry afterward."
"Those who choose to marry are quite rare. Most priestesses remain at the temple even after retirement to continue their service," Priestess Myria replied.
As the other priestesses watched us with curious eyes, we walked past the center of the sanctuary.
"Forgive me if my question sounded discourteous. The matter is simply that important."
Well, no one in this era of Rome was more trustworthy than the Vestal Virgins. The chances of them being swayed by wealth or power were practically nonexistent.
"Just what on earth do you intend to entrust to us that requires such strict secrecy?"
"Here in the Temple of Vesta, you preserve the sacred flame so that it may never be extinguished," I said. "What I intend to entrust to you is no less vital."
"You wish to manufacture this thing within the Temple of Vesta?"
"I would like you priestesses to oversee the final stage of production, but there is no need to do so inside this temple."
If an accident occurred while manufacturing gunpowder here, it would be a catastrophic disaster.
To begin with, the sacred flame alone made the temple the worst possible place for producing gunpowder.
Above all, there was no space to set up a workshop in such a modest building.
"The manufacturing method of the substance I wish to create must remain a sacred secret. It may eventually be revealed one day, but for the next few years at least, total secrecy must be maintained. At the same time, it must be produced in massive quantities."
Right now, the only people who knew the formula for gunpowder were Felix, Vitruvius, and myself.
Now, the Vestal Virgins would be added to that list.
"Mass production while maintaining absolute secrecy... Catching a bird without shooting an arrow sounds easier."
"Which is why I am entrusting only the final mixing to you priestesses. Procuring the raw materials and transporting them will be my responsibility."
What would be the most efficient way to maintain a secret formula?
Back in my time, there was a concept called compartmentalization.
It meant dividing the entire manufacturing process into separate stages so that no single worker could grasp the complete picture.
By segregating the collection of raw materials, refining, and manufacturing into distinct steps, secrecy could be preserved.
However, the final step required blending the ingredients in a specific, precise proportions.
That was the heart of the secret.
And that was precisely where the Vestal Virgins were needed.
"I do not know exactly what you intend to make, but..." Priestess Myria let out a soft sigh. "If you are this concerned with secrecy, you must be using some rare and extraordinary ingredients. What are you using, the tears of a Cyclops?"
"Not quite..."
In truth, very few ingredients were needed to make black powder.
Yet the production process was anything but easy.
I couldn't even begin to guess how many people would suffer through this grueling labor.
"Though quite a few people will certainly be shedding tears."
***
"Are you truly saying we can create this substance—this devastating weapon—using nothing more than charcoal and sulfur?" Felix asked. "Gathering those materials in large quantities shouldn't be too difficult."
"We already have more charcoal than we could possibly need. And sulfur is plentiful as well."
I nodded. Charcoal and sulfur were easy enough to acquire.
Romans already burned massive amounts of charcoal for blacksmithing, heating, and other daily uses.
Sulfur wasn't an unfamiliar substance either.
Sulfur could easily be sourced from volcanic regions like Campania and the Aeolian Islands.
It was already widely used for pest control, medicine, and religious purification rites.
The real problem lay elsewhere.
"Securing the final ingredient will be the real nightmare."
Saltpeter. The most crucial ingredient in gunpowder.
How were we supposed to obtain saltpeter?
"There is a way... though you may not like it"
"Whenever you phrase it like that, Young Master, I get a very bad feeling."
"By gathering feces and urine."
Felix stared at me for a long moment before letting out a weary groan.
"When you made paper, you ordered us to gather old linen rags, and now you're telling me we need piss and shit to make weapons? As you well know, Young Master, our employees aren't here to clean latrines."
"Yes, going door to door to collect waste would be terribly inefficient. But here in Rome, we have public latrines and the Cloaca Maxima."
By collecting waste, we could construct saltpeter beds.
Sprinkling manure and wood or plant ash over soil, mixing it with organic waste and straw, and keeping it moist would eventually yield saltpeter.
"However, that method takes far too long. Even if we start right now, it will take anywhere from six months to two years. "We can make preparations for that later. It's an excellent method for long-term mass production anyway."
"Then what do you propose we do right now?"
"Well..."
From what I had learned in the dream library, natural saltpeter deposits could be found in various caves across Italy.
Hispania, Spain, was also known for having abundant deposits of saltpeter.
However, sending laborers to locate the deposits, extract the saltpeter, and haul it all the way back to Rome would also consume precious time.
Italy didn't possess rich surface deposits of saltpeter like India.
Niter beds or natural cave deposits—either method would take far too long.
With the Gallic expedition scheduled for early next year, we didn't have the luxury of waiting.
There was only one remaining method.
It was labor-intensive, but it was the fastest way to obtain it.
"At least this is something we can find anywhere in Rome."
"Please tell me it isn't waste again."
"It's dirt."
I said, giving a light shrug.
I felt sorry for Felix, but there was no helping it.
"Though, technically, there's plenty of waste mixed into it."
***
As curious Roman citizens looked on, a group of men hurried through the streets.
"This way!"
Spurius hurried along with his colleagues, carrying large clay jars.
They finally came to a halt in front of a grand domus.
Lucius Caesar, dressed in a toga, stepped past them and took the lead.
"There's no need for you to do this yourself, Caesar! We can inspect it ourselves."
"No, it's best if I demonstrate the method myself the first time. By the way, is this the right place?"
"Yes, it is. According to our insurance records, this is the oldest domus in the vicinity."
While Spurius caught his breath, Lucius approached the entrance of the domus.
A slave standing guard at the doorway eyed them warily.
"Have you come by my master's invitation?"
"No," Lucius replied. "However, I would like to speak with your master."
"May I ask your name...?"
"Lucius Julius Caesar."
"P-Please wait just a moment!"
At the name, the slave panicked and bolted inside.
A moment later, a man clad in a toga dashed out, looking just as stunned as his slave.
"Lucius Julius Caesar! What brings you to my humble home?"
"I apologize for the sudden intrusion, Senator Retiarius. If you wouldn't mind, I have a small favor to ask of you."
"A favor? What might that be?"
"If it is not an imposition, may we inspect the soil around your house?"
"The soil? Uh, well... of course you may."
"Thank you."
While the master of the house stood there stammering in utter confusion, Lucius strode right inside.
"Check the kitchen floor, the cellar floor, and the walls near the latrines. If there are stables, check there first. You only need to scrape the very top layer of dirt."
"Just the top layer?"
"Yes. Touch a little to your tongue. Look for soil that tastes salty or sharp."
Lucius bent down, scooped up a handful of earth with his bare hands, and placed a pinch on his tongue.
Watching this, the senator and his slaves gasped in horror.
"W-Wait, that's where our dog always pisses..."
"Good, this is a viable candidate. Collect it and we'll run some tests," Lucius said. "Gather as much of this soil as possible. We'll inspect the other insulae and domus as well."
"Can we truly make a weapon from this dirt?"
"Of course, we can't use it as it is. It must undergo several stages of refining. It will be grueling work."
"Refining... Exactly how, sir?"
"First, we will need horse manure, urine, straw, and wood ash."
Hearing Lucius's explanation, Spurius couldn't help but feel bewildered.
Creating a mighty weapon from dirt, waste, and ash?
Considering all the miraculous innovations Caesar had unveiled so far, Spurius couldn't dismiss the idea outright. Even so, a weapon made from soil and filth was difficult to imagine.
Spurius leaned in and asked in a low, cautious whisper.
"Is it a weapon that drives the enemy away with its stench?"
Young Caesar only laughed instead of answering.
***
"Then let us make the necessary preparations on our end as well."
Following Lucius's visit, the Vestal Virgins took on a new duty.
"Only we priestesses must know the mixing ratios. The temple's dedicated slaves will handle blending the ingredients into the finished compound. Caesar has prepared a secure workshop on the outskirts of Nova Troia, so let us begin there."
Meanwhile, Caesar's laborers mixed the soil scraped from across the city with other ingredients and boiled it in massive cauldrons.
"The stench could kill a man."
"Tell me about it. My wife will be thrilled when I get home smelling like this."
"Cover your mouths with cloth and stir only for your allotted shift! The moment your shift is over, switch places! And keep the place well ventilated!"
As they added water and boiled the slurry, pale white crystals gradually began to form.
"What on earth is this?"
"Dilute it with water and boil it again! We must filter out the salt and other impurities!"
The potassium nitrate refined through this process was transported separately from the charcoal and sulfur.
The Vestal Virgins personally supervised the slaves as they mixed the ingredients.
Under the priestesses' strict oversight, the finely ground powders were mixed in exact proportions.
"A black powder... It looks terribly ominous. Like something a witch would brew for a curse."
"Be careful not to let any spark near it. Caesar said even the smallest ember could ignite a massive fire."
And thus the first batch of Pulvis Vestae—the Powder of Vesta—was created.
However, contrary to Lucius's hopes, the first attempt was nearly a complete failure.
***
"This quantity is nowhere near enough," I said, staring into the clay jar.
After more than ten days of grueling labor, the black powder we had produced wasn't even enough to fill a single small jar.
"To think six wagonloads of soil yielded only this much..."
This was far worse than I had anticipated.
The bottleneck was the nitrate. No matter how precisely the workers followed my instructions, they lacked the experience and skill.
Too many impurities remained, forcing us to discard nearly half of what we produced.
Compared to the mountain of dirt hauled from across Rome, the resulting pile of powder was barely enough to cover a fingernail.
"We need at least several thousand librae before the year ends. We are going to need far more soil."
It would cost an enormous fortune at this rate.
And we couldn't keep scraping dirt from every private house in Rome indefinitely.
Myria was the one who offered a solution.
"I have a thought," Priestess Myria said. "You cannot possibly gather all the necessary raw materials by yourself, Caesar. No matter how much wealth and manpower you pour into it, there is only so much one man can do. Especially when this undertaking brings you no immediate profit."
"I cannot deny that."
With this abysmal yield rate, I would have to continuously sink vast fortunes into the project. And just as Priestess Myria said, it offered no financial return in the short term.
"To scale up production before the refining process is fully perfected, you need vast quantities of raw material. If this truly is a weapon capable of saving Rome, should not all of Rome step forward rather than leave the burden to you alone?"
"Mobilizing the resources and manpower of the entire Roman state would certainly make things simpler."
I considered her words. Perhaps trying to shoulder this burden alone had been the problem all along.
"If we persuade the Senate, we can mobilize the whole of Rome. Though, of course, that will not be an easy task..."
"There is a way," I murmured, watching the fine black grains slip through my fingers. The answer was surprisingly simple.
"We show them the true power of this powder with their own eyes."
I couldn't keep such destructive power under my personal control—not in Rome.
Nor could I recklessly hand it over to people who understood nothing of its nature.
I needed to convince the Senate that the Roman state—not a private individual—had to hold a monopoly over it.
"What do you suppose the Senate will say when they see this?"
I had no way of knowing.
Though only one thing was certain.
This black powder was going to change Rome forever.