Original: It occurs naturally in the peyote cactus (Lophophora williamsii), the San Pedro cactus (Echinopsis pachanoi) and the Peruvian Torch cactus (Echinopsis peruviana), and in a number of other members of the Cactaceae.
Simplified: It occurs naturally in some cactuses, like the Peyote cactus, the Peruvian Torch cactus or the San Pedro cactus.