There's one at least that I wouldn't do again. A few years ago I found instructions for a lobelia tea enema:
"As a tea, [lobelia] is used to induce vomiting. It does this by stimulating massive cramping in any smooth muscle lining it contacts (stomach or bowel). To make an enema of lobelia tea, use 1 ounce of the dried herb to 1 quart of water. Boil the water, then pour it into a teapot with the herb. Cover, and let it steep for 20 minutes. Filter water from leaves. Mix with additional water to bring it up to 2 quarts and adjust the temperature to comfortably warm. Lobelia causes instantaneous, unbearable cramping. It is also reputed to be mildly psychoactive. Whether that's true is hard to say. It does generate a strange, mellow buzz, but that could easily be the endorphins released by the pain of taking it. It is virtually impossible to retain a 2 quart lobelia enema without the help of a retention catheter."
Since I like enemas that cause cramping, I decided to try this one and bought two ounces of lobelia. Following the instructions above, I used half of it to make up 2 litres of the tea and administered it late one night in the bathtub, as my usual practice is. The following is based on notes I made the next day.
"The cramps came on as advertised in about half a minute, and I stopped the flow after about 1.5 litres; but they didn't actually last long, and after about eight minutes I restarted the flow and took the remaining half-litre. I had thought 10 minutes might be as long as I could bear to hold the enema, but in fact there was no problem retaining it for half an hour. Then I let it out — about one litre only, the rest of the fluid having been absorbed.
"But then the real effects started. [Warning: persons with weak stomachs should not proceed beyond this point.] I stood up to have a shower, but abandoned that plan when I suddenly started vomiting. There was no nausea, the only warning was a few sort of half-suppressed hiccups. The vomiting continued for a while, coming in fits every few minutes, after which I felt so exhausted I just lay back in the empty bathtub, feeling cold and uncomfortable and wretched. I could only just summon the energy to turn on a tap to get a mouthful of water. I ran water to clean out the bath, but the plughole got blocked and the water banked up. I knew there was a brush on the floor at the end of the bath that I could use to clear the blockage, but the effort of reaching over to get it was beyond me, and besides, any significant movement of my body seemed to bring on more vomiting. So I just lay there and avoided moving. After a time I tried dabbling with my toes to clear the plughole, which worked, so I ran more water to wash the stuff away. The vomiting became less frequent, but I was too drowsy and exhausted to get up, and was wondering if I would have to spend the rest of the night lying in the bathtub. I started having strange half-waking dreams in which I would see, very clearly, handwritten documents of the kinds I work on in my day job. Eventually I regained a bit of energy and ran water into a bottle and poured it over myself and the sides of the bathtub to clean up. I still couldn't get up, but replaced the bathplug and ran a small bath to keep warm. I lay there for maybe an hour and a half, dozing a lot of the time, and adding hot water whenever I started feeling cold. About half past three, it might have been, I finally felt well enough and energetic enough to get up and dry myself and go to bed.
"The emetic effects are I supposed not unexpected, given the above quote, and I had hesitated to use the stuff on that account. And I guess the strange dreamy visions were the 'mildly psychoactive effects'. But they're not something I would want to pursue for their own sake. And I won't be using it again. I threw out the rest of the herb with the rubbish."
[Reviewing that account after about four years, I think the instructions may be wrong in attributing lobelia-induced vomiting directly to irritation of the GI tract. The cramping stopped pretty quickly, and I had expelled the solution long before the vomiting started. I suspect it is more likely to act via the bloodstream on the vomiting centre in the brain.]