The practices grouped under this heading share a shape without sharing an origin. A person is prepared for days or weeks before anything is taken, usually by a restricted diet and by abstention from sex and from salt; the plant is then taken under the direction of a specialist who has served a long apprenticeship, in a setting the specialist controls; and the specialist works throughout with sound, most often sung, which is treated as the instrument that steers the experience rather than as accompaniment to it. Afterwards the person is received back by a community that has an account of what happened and a place to put it.
Every part of that sequence matters to the people who do it, and the part most often dropped when the practice travels is the last. A session without the community that interprets it is a different thing from the practice as its holders describe it, whatever plant is involved.
These are living traditions with living authorities, and several of them are closed. Bwiti initiation in Gabon, Huichol pilgrimage in Mexico and the ceremonies of the Native American Church are held by specific peoples who decide who may take part. This atlas records what such practices are and where they are held, because that is public knowledge that their holders have themselves put into the record. It does not set out how to conduct one, and it does not treat the plants as available techniques. The distinction is not squeamishness: the traditions themselves make it, and the training they require is the part that cannot be summarised.