My father--a physician--used to talk about croton oil. "One drop will clean out an elephant." Apparently made from the croton bush. A 'powerful purgative'. In medical school in the 1930s, it was considered highly amusing to distract someone and put a tiny drop of croton oil in his drink. You had to be careful, because too much could kill the victim.
Evidently croton oil was once available over-the-counter, but no longer. I guess they didn't have many dyspeptic elephants...or mischievious medical students.
--Boris