Ritual plant use very rarely leaves durable evidence. Yopo is the exception, and it is the reason its antiquity is better established than that of almost anything else this atlas describes.
Snuff-taking requires equipment: a tray to hold and mix the powder, a tube to inhale or blow it, a spatula, a container. These are made of wood, bone and stone, they are frequently carved with elaborate iconography, and in the dry conditions of the Atacama and other arid burial contexts they survive. Torres and Repke assembled the corpus, which spans a very wide area of South America and a range of dates running back several thousand years, and chemical residue analysis has in some cases confirmed what the trays held.
The equipment carries a second kind of information. Because the trays are carved and their imagery is stylistically datable and regionally distinctive, they let the spread of the practice be traced across cultures and periods in a way that oral tradition cannot. The iconography frequently shows the same fanged and transforming figures that appear in San Pedro contexts, which suggests a shared visual language for the state rather than for the plant.
A southern relative, Anadenanthera colubrina, was prepared identically under the names vilca and cebil, and appears in Andean and northwest Argentine material. The two species are often confused in older literature, so a source that names only the practice and not the species should be read with care.