(A larger monograph by Lloyd can be found at: http://www.swsbm.com/ManualsOther/Physostigma-Lloyd.PDF)
Physostigma, Calabar bean (Physostigma venenosum), is the fruit of an African vine growing near the mouths of the Niger and the Old Calabar Rivers, Guinea, where it furnished one of the ordeal tests of the pagan tribes of tropical Western Africa. The seed is therefore known as the "Ordeal Bean," and was administered in the form of either an emulsion or infusion, as the case might be. It was introduced to England by Dr. F. W. Daniel (182), about 1840, its method of use being again mentioned by him in a paper read before the Ethnological Society, 1846. Professor Balfour (36), of Edinburgh, obtained the plant from the Rev. W. C. Thompson, a missionary to the west coast of Africa, and described it in a paper read before the Royal Society of Edinburgh, including it also in his "History of Plants." Its power of contracting the pupil of the eye was discovered by Dr. T. R. Fraser (246) of Edinburgh. Its power of paralyzing the action of the heart, was indicated through its native employment as an ordeal poison.