Hi. I was searching and I found that the inventor of the "Ashes on arm" trick is John White (1718).Originally posted by mizar:
The originator is unknown, but we do know it's pretty old. We're talking 1500's old. See Prevost's Clever and Pleasant Inventions.
Prevost says pee should be used. So, if you're shooting for historical accuracy, mystery and wonder is only a six-pack away. Of course, this ain't for everyone (sorry asparagus lovers).