3,4,5-trimethoxy-ß-phenethylamine

Mescaline was made popular with the use of peyote, (l. williamsii) but, by and large, most mescaline these days is derived from the San Pedro cactus (trichocereus pachanoi).

It has higher concentrations of mescaline in it, and, more importantly, is a helluva lot easier to grow. Not only that, but the cactus is used throughout the United States and other countries as a decorative plant. If you live in Arizona, odds are, you've seen one. Preparing mescaline from San Pedro is surprisingly easy, and although I would like to node the procedure, certain new internet laws prohibit it, since it's illegal in many countries.

Mescaline is one of the most-researched psychotropic drugs ever, and since the 1950's, mescaline has been used as the benchmark of comparison to other psychotropics. It's not at all uncommon to see drug effect reports that say "intensity: 2x mescaline" or "duration: 1/2 mescaline". It's use goes back to Native American shamanistic ceremonies, much like Salvia Divinorum and has no known adverse side-effects. Placebo effect and psychosomatic responses are always possible, of course.

On a side note, while general mescaline possession is illegal in the United States, there is a condition that allows you to possess and consume it: The Native American Church. Unfortunately, you have to be a member, and they won't let you join without being Native American.