Mesaline, a substance extracted from a San Pedro cactus, has been used as a hallucinogen by many priests. Thought to possess a hypnotic power, the cactus was used largely to put people into a trance, and be put onto a state in which the priest's suggestions can make an impact. Thus this substance was used to control large groups and religious sites.
As with all drugs, mesaline may provide a trance-like state, but due to an imballance of chemicals, may lead to illness.