The Red Cherub's Datura Central

Known as the "Lady of the Night", datura is the "Devil's Herb" mentioned in Carlos Castaneda's books on Mexican shamanism. It belongs to one of the most toxic sub-families of plants known to man, including such historically (dis)reputable plants as the Deadly Nightshade, the Mandrake root, and Henbane. These plants produce deliriant states in sufficent doses.
The cause of the psychoactive effects are the presence of tropane alkaloids(scopolamine, atropine, hyoscyamine) Dramamine is related to scopolamine. The tropanes have many uses medicinally in controlled doses.

Datura is legal to grow and possess in the UK and US, although the state of New Jersey (USA) apparently has a law regulating the growth of datura stramonium.

Common side effects of datura ingestion include dilated pupils, parched throat, flushing of the skin, increase in body temperature, light-headedness, complete or partial dissociation from reality, as well as a dangerous increase in heart rate. Death can also occur by respiratory failure
One of the most perculiar traits of these plants is the hallucinations and other consciousness-altering effects they cause. Intoxication may last several days, whereby one can become immersed in interpolating dream states. Talking to people others can't see, as well as out-of-body experiences, are common. Datura has been used historically around the world in ritual settings, including India, North America, and possibly Europe. (We know other plants in this family were ingredients in witch's sacraments in the Middle Ages.)

The Datura Dosage Database has been removed. The alkaloid content in datura species has the potential to vary widely from plant to plant, and even within the same plant, depending on a variety of conditions. In addition to this, individuals have different tolerances to datura, so that a singular batch might hardly affect one person, while making another seriously incapacitated.

Generally what this means is that the only way to insure safe dosage is to start with ridiculously small amounts.
In my case that meant 10-20 seeds as a starting dose for every new batch (meaning a batch picked at a separate day, or time of day).

My research on datura will be posted here soon, so please, stay tuned folks!

Erowid's Datura Vault
Crazy Kieri's Domain of Datura
Cornell University's Datura Page on datura botany