Peyote is a small, spineless cactus, Lophophora williamsii, whose principal active ingredient is the hallucinogen mescaline. From earliest recorded time, peyote has been used by natives in northern Mexico and the southwestern United States as a part of traditional religious rites.

The top of the cactus above ground--also referred to as the crown--consists of disc-shaped buttons that are cut from the roots and dried. These buttons are generally chewed or soaked in water to produce an intoxicating liquid. The hallucinogenic dose for mescaline is about 0.3 to 0.5 grams (equivalent to about 5 grams of dried peyote) and lasts about 12 hours. While peyote produced rich visual hallucinations which were important to the native peyote cults, the full spectrum of effects served as a chemically induced model of mental illness. Mescaline can be extracted from peyote or produced synthetically.