Datura

Datura (also known as Jimson Weed, Devil's Apple, Thorn Apple, Stinkweed, Devil's Trumpets, Malpitte, Toloache, and Moonflower) is a night-blooming plant whose parts (especially the seeds and roots) contain an anticholinergic deliriant drugs, similar to Benadryl, except that it grows everywhere and gives you a bad trip 99% of the time. It is usually used by retarded back-country ranchers, faggot hippy "naturalists" into "entheogens", and dirt-poor white trash who can't afford better hallucinogens. Unlike most hallucinogens that may cause a psychotic episode, with datura the psychosis IS the point and will make you batshit insane for a day or two. 9 times out of 10 you will end up eating way too many seeds, and run naked from the cops screaming about how YOU TOTALLY SAW GOD AND IT LIKE BLEW YOUR MIND MAN! Or at least that's what people told you happened when you wake up 3 days later, naked in a Mexican prison with blood on your ass. Also, for several days after eating the seeds, you will be rewarded with painfully dry mouth, extremely fucked-up vision due to pupils dilating the fuck out, excessive sweating, nausea, and a raging headache. Alcohol and pretty much all other drugs will generally make your condition much worse, so you're stuck suffering (again, the point). It's also very easy to overdose on, and plenty of people have died from it, but they're obviously pussies. Witches used to make ointment out of boiled fat from Jewish children and ground up seeds, and rubbed it in their skin,anuses,and vaginas because they absorb less of the deadly poison than eating them. If you want to do datura, but don't want to have a heart attack, this is the best method, because to this day datura is an active ingredient in motion sickness patches, srsly.

An artist's rendition of a Datura trip. Yours probably won't be this cool, however.

Belladonna (Deadly nightshade)

Belladonna is another anticholinergic drug related to Datura. Glory unto White Jesus! Turns out, any plant which will kill you in large doses gets you high in slightly-less-large doses. Who'd a thunk it? Belladonna, also known as deadly nightshade, contains a potent anticholinergic deliriant which is imbued with the same wonderful magicks as Datura. If you can manage to get the right dosage, rather than dying a horrible death, you will be rewarded with a horrible trip full of spiders and deadly anal penetration from your favorite childhood toys.