Despite the acronym making this sound like maybe a more synthetically concocted compound, DMT (Dimethyltryptamine, or more fully, N,N-Dimethyltryptamine) is in fact one of the most common naturally occurring psychedelics. It is found in the leaves, roots, and bark of many plants including trees, shrubs and grasses. The variant 5-MeO-DMT (5-Methoxy-N,N-Dimethyltryptamine) is even found excreted from the skin of certain species of toad. Not only that, research suggests that DMT is also produced in the human brain, particularly when dreaming.
The fact that DMT is already a part of our neurochemistry, rather than a substance similar to or mimicking something in the brain, may account for it's incredible power. Reckoned by many to provide the most intense of all psychedelic experiences, it is also notable for the speed of its action and the relatively short duration of its effects. Smoked, or even injected, the DMT experience lasts only a matter of minutes.
Having said that it is one of the more commonly occurring plant psychedelics, the extraction of DMT in a usable form is not straightforward, at least not in comparison to Salvia divinorum or psilocybin mushrooms for example, which can be pretty much ingested as found. Certainly, isolation of the substance into a purer crystalline form for smoking would require some chemistry knowledge. There is information about this on the web, but I have never looked much further into it other than noting that there are also a lot of conflicting opinions.
There are two main problems.
1. Although DMT occurs in a number of plants, the concentrations are typically so low that the material cannot be ingested directly.
2. Stomach enzymes break down DMT so it can't normally be orally ingested on its own.
For DMT to work orally, the addition of something referred to as a monoamine oxidase inhibitor (MAOI) is required. MAOIs such as harmine inhibit the production of the stomach enzyme and this allows orally ingested DMT to become effective.
Terence McKenna gave eloquent descriptions of his DMT experiences. The following MP3 audio download link is highly recommended.
DMT experience (size: 1.38 MB)