[Jimson Weed, Devil's weed, Devil's cucumber, Thorn-apple, Pricklyburr,
Angel's trumpet and Devil's trumpet, Datura stramonium, also
similar Datura wrightii]
A common weed here in Southern California, this plant is far more deadly than the Deadly Nightshade. It's mind altering powers are so awesome even people heavily into "recreational substances" have generally shunned it. All parts of the plant are highly toxic.
Unlike psilocybin or LSD, which cause sensory distortion, datura is a true hallucinogen, transporting the user entirely into another reality with little or nothing of this reality to hang on to. An additional problem is that there is little margin between the effective dose and a fatal dose. Persons who have heard of this plant but not studied its use thoroughly often take a dose and find no effect - so they take a second dose of similar size and die.
The expert advice is "Don't", but if you do be very, very careful and have adequate and adequately briefed support staff on hand, strong enough to control you and with access to emergency care. Keep in mind that if the user's personality is not rock solid (does not describe most recreational substance users) it's likely to become completely unglued.
More on Nightshades.
The photo to the left is of Datura Plants, one of which has a nearly
mature seed pod. These plants are pollinated by Sphinx Moths (Hawk
Moths), so strong and fast they seem more like birds than insects.
They can even hover like a humming bird. The moths are also toxic,
because in their lava stage they fed on toxic leaves of the Datura
plants.