Mescaline powder is a psychedelic hallucinogen obtained from the small, spineless cactus Peyote (Lophophora williamsi), the San Pedro cactus, Peruvian torch cactus, and other mescaline-containing cacti. It is also found in certain members of the Fabaceae (bean family) and is produced synthetically.

People have used hallucinogens for hundreds of years, mostly for religious rituals or ceremonies. From the earliest recorded time, peyote has been used by natives in northern Mexico and the southwestern United States as a part of traditional religious rites. Mescaline leads to rich visual hallucinations which were important to the native peyote cults. It has an effect that is similar to LSD or psilocybin (magic mushrooms), other hallucinogenic drugs.