Amanita muscaria, a hallucinogenic mushroom with a crimson cap growing on all continents save South America, Antarctica and Australia. It has over fifty different species and the fascinating property of passing through the body almost completely unmetabolized, leading to very potent urine. Native Siberian tribesman, who had spiritual rituals centered around the fungus, thus had a very good excuse for drinking urine, a process which was repeatable for five cycles before the drug lost its potency. The reindeer of the tribesmen also enjoyed the intoxicating urine, and reindeer could be attracted from far away in such a fashion.
It is speculated that the fly agaric mushroom is the identity of the drug Soma, described in the Rg Veda. Additional weird tales about fly agaric include Napoleon On Drugs in Siberia and the origins of Santa Claus.
The fungus, unlike most hallucinogens, causes the user to experience great physical movement.