The San Pedro ceremony of the north Peruvian coast is a healing rite rather than a visionary retreat, and its structure is unusually consistent from one practitioner to the next.
The cactus is cut into slices, boiled for hours into a thick bitter decoction, and drunk around midnight. The centre of the ceremony is the mesa, a cloth laid on the ground and arranged with objects: staffs, swords, shells, stones, images of saints, bottles, archaeological pieces picked up from old sites. The mesa is divided into fields, commonly a left side associated with disorder and illness and a right with order and healing, with a mediating centre, and the curandero works across it through the night, rattling, whistling, invoking both Christian saints and the mountains and lagoons of the region.
The patient is there to be diagnosed. Much of the work is identifying the cause of an affliction, frequently understood as dano, harm sent by another person, and then removing it. Tobacco is taken through the nose, plants are rubbed and blown, and a cleansing with a guinea pig or an egg may be used to read the body.
The plant is not the ceremony. It is what allows the curandero to see, and the patient may take less of it than the practitioner does. This is a working craft with clients, fees and reputations, not a retreat, and it has functioned continuously alongside Catholicism for centuries.