Psilocybin and psilocin
Psilocybin and psilocin are the active alcoloids from various kinds of mushrooms, especially Psilocybe Mexicana, though there are types of European mushroom which also contain this substance. Psilocybes are used by Mexican healers (curanderos). Psilocybin 'mushrooms' also appeared on the market in Europe in the 1970's but at first they proved to be nothing but instant mushroom soup to which LSD had been added. Later on the genuine dried psilocybe mushrooms became available.
Psilocybin is an indolamine. Its effects are not significantly different from those of LSD. The effective dose is approx. 10 mg.
For more information see the drugtext psychedelic library