It occurs naturally in some cactuses , like the Peyote cactus , the Peruvian Torch cactus or the San Pedro cactus . 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 plant family .