My new hobby: using my lovely institution access to EEBO to look up random subjects from a course I took on History of Science. Here's a mention of usnea, which is moss taken from the skull of a hanged man, from a text published in 1631:
Scull-mosse, or Bones, (saith Doctor Fludd,) Mummy, and the Fat of Man (the especiall ingredience) comprehend the corpor all perfection of man, and so are apt to heale, by reason of a naturall Balsam resting in them, sympathizing with the hypostaticall Balsam residing in the living Man.
"Mummy" here being dried out human flesh, it appears; Doctor Fludd made a balm out of these things to treat injured people, a la weapon salves.
The premise of weapon salves is that when a person is injured by a weapon, there forms a Sympathetic link between that weapon and the person. Now, when someone gets their arm hacked open with a sword, one's first instinct would be to treat the arm-- but because of this sympathetic link, one other option would be to apply your treatment to the sword instead. There was a lot of argument back and forth about this theory, but the weapon salve people held their ground for a while, in part because their method was rather successful. This is, of course, because medical balms at the time were made from bear fat and chunks of rotting corpses: weapon salves worked better because they put the rotting fat salve on the sword instead of the person's arm, which in the weapon salve treatment was simply cleaned and wrapped in fresh bandages each day.
One wonders what seemingly reasonable (and in fact genuinely successful) methods of today will look equally bats to future generations.