The name derives from the fact that in Christian mythology Saint Peter holds the keys to heaven, and in the shamanic traditions of the Peruvian Andes, San Pedro cactus is a key to heaven.
In the famous book on psychoactive plants “Plants of the Gods” the authors offer this quote about San Pedro cactus from a shaman. “the drug produces .. drowsiness or a dreamy state and a feeling of lethargy..a slight dizziness..then a great vision, a clearing of the faculties..It produces a light numbness in the body and afterward a tranquility. And then comes detachment, a type of visual force..inclusive of all the senses..including the sixth sense, the telepathic sense of transmitting oneself across time and matter…like a kind of removal of one’s thought to a distant dimension.”
San Pedro, containing mescaline, Mckenna associated with a more grounded, heart-centered, and expansive clarity compared to the hyperdimensional intensity he attributed to DMT or the linguistic, teaching presence he found in mushrooms. He saw mescaline visions, including those from San Pedro, as luminous, structured, almost architectural—revealing pattern, symmetry, and the deep aesthetic order of nature.
He also connected mescaline traditions back to figures like Aldous Huxley, whose descriptions of “Mind at Large” resonated with McKenna’s sense that these plants dissolve the filtering mechanism of ordinary perception. In this sense, San Pedro was a doorway into what he sometimes described as the “felt presence of immediate experience,” where the world discloses itself as intrinsically meaningful, radiant, and alive.
At the same time, he tended to frame mescaline plants as somewhat less “alien” than tryptamines. Where DMT launched the psyche into contact with radically Other intelligences, San Pedro seemed to him to deepen immersion in this world—enhancing connection to landscape, body, and emotional field. It belonged to Earth in a very direct way, a solar sacrament rather than a hyperspatial rupture.