Peyote (Lophophora Williamsii) is a cactus found primarily in dry regions of Mexico and State of Texas. This cactus contains psychoactive alkaloids, but mescaline is the most important. For its psychedelic effects, the dried tops of the cactus, also known as “buttons”, have been used for centuries by Native Americans in religious ceremonies and for the treatment of various physical ailments. Mescaline is one of the oldest hallucinogens known by man. His clinical effects are similar to psychedelics like LSD or MDMA, and it has historically been used as a reference standard in hallucinogen research. A full dose of mescaline (200 to 400 mg) has a long duration of action, with peak effects 2 to 4 hours after consumption, declining over the next 8 hours. Many of the studies done with mescaline also included other psychedelics, like LSD or psilocybin; we decided to include these polydrug studies for his relevance anyway.