By far the worst is Jimson Seeds...
I could tell you story's that are insane from these...
I have a few friends that have died from this shit...
Used it several times over 30 years ago and I would not touch this stuff if my life depended on it now.
Short explanation of them if you don't know what they are.
Notorious for its toxicity, Jimson Weed is a large flowering plant with the genus Datura and the family Solanaceae. It has long white trumpet-like flowers. Its seeds grow in pods and can be consumed (or its leaves can be smoked) to produce an extremely potent psychoactive effect.
A typical dose is 5 to 7 seeds, but it has been reported effective in as little as 2. An overdose can cause delirium, delusions, paralysis, stupor and death. This is due to its dangerous combination of atropine, scopolamine, and hyoscyamine.
Its effects are said to always trigger a 24 to 48 hour anticholinergic delirium, which basically means the user is incapable of distinguishing fantasy from reality - NOT to be confused with hallucination in which the user may know is false interpretation. Overall, no matter how bizarre things get, the user will still find the twisted reality credible.
Users report when they are not hallucinating, they still are susceptible to abnormal actions which the user perceives as normal, and things the user would never do seem like just an everyday activity: ie. Rearranging furniture into one corner of the room in a very obviously impractical way, but the user, completely aware of what they are doing still does not see it as abnormal and may believe they are doing something useful.
Common Names: Devil's Apple; Thorn Apple; Stinkweed; Devil's Weed; Malpitte; Moonflower; Toloache; Angel's Trumpet; Daemon's Trumpet