I just did some reading up on Amanita Muscaria mushrooms. Here are some interesting things I learned.

They're toxic, but rarely kill people.
In some tribes it's not uncommon for the shaman to consume Amanita Muscaria and then have the rest of the tribe drink his urine, because the active ingredient of Amanita Muscaria is released in urine but the toxins are not.

What I want to know is, how did they figure that out in the first place? Like, back before science existed. Someone ate a mushroom and then someone drank their piss for fun?