Cebíl, Cohoba, Vilca, Yopo, Ñopo
The seeds, or more correctly, beans, of two distinct species of Anadenanthera trees are used for their psychoactive effects in Southern and Central America. The first, A. peregrina, is known under the names Yopo and Cohoba (amongst others). The second, A. colubrina, is known primarily as Cebíl. Due to the similarity of their active constituents (5-OH-DMT or Bufotenine, 5-MeO-DMT, DMT), and the sometimes indistinguishable practices by which they are used, I have considered them here together as one diverse entheogen.
Traditional Snuff Preparation
The beans are toasted over a fire or in a pan, they will pop as the cases split. The seeds should be heated further until they are thoroughly dessicated, making sure that the seeds are not burned in the process.
Once the seeds have cooled, the brown outer case is removed and discarded.
The inner flesh of the beans are them thoroughly ground or pounded in a metate, or motar and pestle. Once a fine powder has been produced, the powder is sieved and any large particles are removed, re-ground and sieved again. The final powder should be the consistency of tobacco snuff, or finer.
Next, snail shells are pounded to the same consistency. They are heated over a very hot fire until they turn white. I believe this is identical to the process of turning Calcium Carbonate into Calcium Oxide (quicklime, caustic lime or CaO). For the modern psychonaut, the lime paste used for Betel chewing would probably be a more convenient source of lime.
Once the bean power and lime powder have been prepared, they should be mixed together. The chosen ratio seems to be at the discression of the Shaman in question. But a ratio of 1 part lime to 2 parts seeds seems to be normal. The greater the ratio of lime, the more caustic the snuff will be, and thus will couse far more discomfort and irritation of the nasal passages. Over 50% lime is probably too much.
When the powders are thoroughly mixed, the snuff is ready for use.
Aminiapä & Tupari Snuff Preparation Technique
Here is another method, reported by Franz Casper in 1953 and printed in the Swedish journal Ethnos in 1963.
"Then the loose seeds were not roasted, but pounded and formed into a pancake. This pancake was held between pieces of bamboo and roasted over the embers. Then the jungle Shaman-Apprentice pounded the pancake in the small, vertical wood mortar, and pulverised the powder in the earthen bowl.".
Or if you want to read it in the original German:
"Dabei wurden also nicht die losen Samen geröstet, sondern diese im rohen Zustand gestampft und dann zu einem Fladen geformt. Dieser Fladen wurde zwischen Bambussplitter eingeklemmt und über der Glut geröstet. Dann stampfte der jungle Schamanen-Aspirant den hart gewordenen Fladen im kleinen, vertikalen Holzmörser und zerrib das Pulver in der irdenen Schale.".
[Franz Casper - [cit.] Ethnos 1963:1]
The snuff is then ready for use.
Otomac Snuff Preparation Technique
This method is from the Otomac tribe of Venezuela, who apparently threw "themselves into a peculiar state of intoxication... by the use of the pwoder [sic.] of niopo".
"[The Otomac] gather long pods of mimosacea, which we have made known by the name of acacia niopo [Anadenanthera peregrina], cut them into pieces, moisten them, and cause them to ferment. When the softened seeds begin to grow black, they are kneaded like a paste, mixed with some flour of cassava and lime from the shell of a helix [snail], and the whole mass is exposed to a very brisk fire, on a grate of hard wood. The hardened paste takes on the form of small cakes. When it is to be used it is reduced to a fine powder, and placed on a disk five or six inches wide. The Otomac holds this disk, which has a handle, in his right hand, while he inhales the niopo by the nose...".
[Von Humbolt - [cit.] Wassen in Efron et Al 1979]
Magic Fingers Too
It's worth noting, that according to Jonathan Ott , it's not just the beans of these leguminous trees that are used traditionally for snuff. The leaves also have been reported to have been used, and the phytochemistry says the leaves contain DMT as their primary ingredient.