Psilocybin is the main ingredient found in several types of psychoactive mushrooms, making it perhaps the best-known naturally-occurring psychedelic drug.
Although psilocybin is considered active at doses around 3-4 mg, a common dose used in clinical research settings ranges from 14-30 mg. Its effects on the brain are attributed to its active metabolite, psilocin.
Psilocybin is most commonly found in wild or homegrown mushrooms and sold either fresh or dried. The most popular species of psilocybin mushrooms is Psilocybe cubensis, which is usually taken orally either by eating dried caps and stems or steeped in hot water and drunk as a tea, with a common dose around 1-2.5 grams.