What a trouser-load.
BTW, didn't the Assassins get their name from using hashish? Not so sure you're right on that one, though one of the enduring biological mysteries is related - the question of how cocaine metabolites could have been found in Egyptian mummies when the coca plant existed solely in the New World.
On the trouser question, apparently there was very recently a discovery of a burial in territory that is now China, of two men, wherein trousers were found...supposedly the oldest documentable use of trousers discovered so far.
It's pretty well established that most of the Amazon tales are balderdash concocted by the Romans and Greeks/Hellenics as a bugaboo scary story, on a par with the cyclops, centaurs, sea serpents, dragons, and such. Any statues that survive are the Greek and Roman embodiments of that myth, like trying to reconstruct what our society was like from Bruce Willis movies 2500 years from now. All the real evidence is that there may well have been an actual people who gave rise to the myth, mostly likely somewhere toward the eastern end of the Black Sea, and there is a tiny element of truth in the Classical legends, but something on the close order of about 1% truth and 99% total bullshit.