Fun game!
I would go the Joseph Smith x Christianity route:
I would first spend a bit of time familiarizing myself with the politics and religion of Rome (what gaps do I have in my modern knowledge?).
I would write a holy text claiming to be a divine revelation; it would be written on large tablets of aluminum (aluminum synthesis should be possible, and it is a plausible "unearthly material"; if my awesome knowledge makes it possible to make a metal that would be slightly more impressive or easier to make than aluminum, good). The front face would be readable etchings, but the back face would be usable for printing, so with a simple enough apparatus copies of the text could be easily created.
The text itself would be written in poetic Latin, claiming to be a revelation from a politically acceptable and "plausible" divinity, and saying nice things about the established Roman clergy (the goal isn't to turn them against me), claiming that I am a special seer sent by the Gods. The text would also contain exhortations in various languages (in their own scripts) exhorting Hebrews, Persians, etc. to bow down before the might of the Romain Empire, it's Law, and it's Gods, presented in a non-insulting way (i.e. "Yahveh is Jupiter", not "Abandon your Idols, Heathens!").
The tablets would also contain relatively detailed maps of the world, and especially of the Mediterranean, as well as instructions on how to build more accurate astrolabes to find one's way at sea. I would also introduce a system of decimal numerals, which makes calculations way easier than with roman numerals, as well explain useful things like double-entry bookkeeping, the principle of a joint-stock company, etc.
The tablets would also contain promises of everlasting life for those who worship the Gods the right way, as well as recommended rituals that may be slightly different from the established ones. There would be more detail on the afterlife, the bad things that will happen after death to those who do bad things (damage a copy of the tablets, disrespect a priest, kill a roman soldier, break Roman Law, etc.), and the good things that happen to those who do good things (copy the tablets, teach others about the new rituals, learn the new numerals, make offerings in the local temples, etc. Again, the goal is not to get in the way of the local religion, but to maximize memetic virulence. Some exhortations of how all will be equal in the afterlife could be good for appeal to the popular classes.
The tablets would be numbered to make it more likely that all are propagated together.
The tablets would also contain some esoteric nostradamus-like bullshit, as well as some encrypted stuff - well encrypted. Decrypted, it they would give instructions on how to read a hidden message in the whole tablets (like, for each page, follow the Fibonacci sequence (which would be explained in one of the tablets) to get a set of letters, cycle all those letters alphabetically), and the secret message would that oh in fact, the Gods want Emile to be the emperor, or they will rain fire upon the world. I would ideally have several secret messages encrypted through the tablets (some claiming the emperor is evil and needs to be overthrown, some claiming he needs to step down, some saying that now that he's dead I should take his place, some saying that when the big volcano explodes in wherever it's the sign that the end is near, etc.)
I wouldn't claim to myself know about all those neat things - I would extract them from the tablets, after much time and effort - I'm not dangerous, I'm just a vessel! But through divine revelation I can interpret parts of the tablet, especially the nostradamus-y bits.
That should be sufficient for me to secure a safe and influential position in the official Roman Religion, surround myself with disciples to help me in my study. From then, the best course of action may be to isolate myself with devoted disciples in some mountain or something, show all signs of being inoffensive, "discover" the encrypted revelation that I am in fact the emperor, only show it to an inner circle of disciples, develop firearms, and either assassinate the emperor and take his place, or wait for him to die and reveal the revelation. That would also be the time to release an explanation of the decrypting method to the rest of the world, so that all those copies of the tablets become manifestos in my favor.
The firearms (and things like mustard gas, and whatever other military technology is possible) should be enough for a bunch of fanatics to hold the palace in case the army has objections, and once it is apparent that I have broad enough popular support because of the tablets, the rest of the Empire shouldn't insist too much and accept me as emperor.
Some refinements, after reading other ideas in this thread:
Split the work into several books: one targeting merchants and navigators, one targeting scholars and lawyers, one targeting priests, one targeting noble families, one targeting plebians, a secret one targeting the army, etc. (the details could vary depending on which targets are the most valuable) The books would reference each other (except the military one) as a marketing ploy.
The secret military book would be written in an alternate alphabet (simple replacement of letters with strange symbo
A recent discussion post has compared the difficulty of an AI destroying modern human civilization to that of a modern human taking over the Roman Empire, with the implication that it is impossible.
The analogy has a few problems: first, modern humans don't have much greater raw intelligence than the Romans, only a bit more knowledge and tools; an AI would have a genuine intelligence advantage. Second, a high-tech civilization like ours offers many more ways for a genius to cause chaos than existed in classical Rome: it's more plausible that you can throw a few existing technologies together to create a superweapon than that Ptolemy could have done likewise, and there's no ancient Roman equivalent to hacking a nuclear launch system.
But taking over ancient Rome might serve as an interesting upper bound on the difficulty of an AI taking over modern civilization. And it's a theme of Harry Potter and the Methods of Rationality that rationalists should be able to come up with creative solutions to seemingly hard problems. So if Professor Quirrell offered it as an extra credit assignment, how would you take over Rome?
Here are the rules:
- You are thrown back in time to the year 1 AD. You can choose to arrive anywhere in the world, but your method of arrival cannot itself give an advantage (you can't appear in a flash of light in the middle of a religious ritual or anything).
- You do not start with Roman citizenship or any other legal record of your existence.
- You keep your original physical characteristics, including sex, height, and fitness. You will appear in period-appropriate dress of your choosing, and can't carry any artifacts with you. You may start with enough money to live a patrician lifestyle for a year.
- You are intellectually near-perfect. You know all human knowledge as of 2012. You speak fluent Latin (and all other languages of the day) and can orate as eloquently as Cicero or Demosthenes. You are a tactical genius of the order of Caesar and Napoleon. And you have infinite willpower and goal-directedness: aside from human necessities like sleep or food, you need never rest.
- You win if you either become Roman Emperor (and are acknowledged as such by most Romans), or if a state you control conquers the city of Rome. You lose if you die, of old age or otherwise, before completing either goal.