There is actually a thriving market on ebay for mimosa hostilis root bark, phalaris grass and any number of sources for tryptamines (DMT). You can do a VERY simple acid base extraction (translated, dump your ground up goo in a solution of sodium hydroxide, then a nonpolar solvent, then put in a little muriatic acid and separate the layers... no chemistry knowledge needed), and allow to evaporate, and you have the makings of an INTENSE hallucinogenic experience. Same goes for morning glory seeds, certain kinds of cacti, and various other plants. Further, you can obtain your own hallucinogenic mushroom spores LEGALLY and grow them (ILLEGALLY) in a substrate you prepare from common materials. Again, all this stuff you can buy right off the internet, legally, including (in some states) salvia divinorum, a legal smokable intense hallucinogen.
You can also do poppy seed extractions for opiates, but you need a little more expertise for that.
These are all from legally obtained sources. NOTE: the preparation of these items is EXTREMELY illegal and will land you in jail if you are caught.
I haven't done any of this kind of stuff in 30 years, but it is amazing to see what I thought was "secret" info for a clandestine number of acid cooks is now available to anyone who can find google.