Ideally theses mixtures should not make you cough incessantly, but just cough effectively once in a while, bringing up some of that excess phlegm. Jimson Weed Seeds, Datura sp. One good reason to smoke an herb as a preferred method of ingestion is regulation of dosage. You can smoke an herb that is very strong and regulate the dosage safety. The difference between medicine and poison is dosage.
Many plants are too strong to take internally safely.
If you take a tea, it may take half an hour or more before you can tell how strong of a dosage you took. At that point it is too late to take less. When you smoke an herb the effects or side effects become apparent quickly. If the herb doesn't agree with you, you can stop before overdosing. Jimson weed is definitely a strong hallucinogen, poison, medicine any way you look at it.