Any drug that can cause a person to hallucinate.

This hallucinogenic drug is produced naturally by a wide variety of plants and fungi. It can produce vivid hallucinations in the human brain.

This cactus grows in Texas and Mexico. It produces a psychoactive drug called mescaline, a hallucinogen sacred to Indigenous American tribes, who have developed ceremonial uses for it. After he gains an understanding of its sacredness to Indigenous Americans, Pollan chooses to forego an experience with peyote and instead uses a synthetic in pill form and eventually participates in a ceremony using Wachuma.