Nothing impresses as much as a deadly weapon. Learn to make Gunpowder. If there were wise men, teach them the value of Zero. If everything else fails, claim

Nothing impresses as much as a deadly weapon. Learn to make Gunpowder. If there were wise men, teach them the value of Zero. If everything else fails, claim to be a prophet and produce a book with some vague moral values. Make the claim that you are from the future, one of the cardinal dogmas.