Ordeal or Calabar Bean (physostigma venenosum) is native to an area 
of Nigeria known as Calabar. The poisonous seeds of the calabar bean 
were used as an ordeal poison to identify witches or those possessed 
by evil spirits. The accused were made to take drink made of the beans. 
The accused were declared innocent if they survived otherwise guilty 
if they died of respiratory failure. The trick to survive the ordeal is to 
take big gulps of the drink to make one sick and regurgitate the poison. 
The active ingredient of the ordeal bean is the alkaloid physostigmine 
that prolongs the activity of acetylcholine by binding to acetylcholin-
esterase. It is used in insecticide and nerve gas in chemical warfare. 
In ophthalmology, it was used to treat glaucoma for over a century. 
Nowadays, it is mainly used for myasthenia gravis.