Author: Michael Hunt, MD Educational Pearls: Here is a list of some very toxic natural substances:     #5: Tetrodotoxin: Found in pufferfish and other aquatic species #4: Ricin: made from castor beans #3: Mercury: natural element absorbable through skin and gloves #2: Batrachotoxin: found on poison dart frogs #1: Botulinum toxin: produced by Clostridium botulinum and causes a descending paralysis Editor's note: batrachotoxin is thought to be accumulated by the beatles and other insects dart frogs eat - those in captivity therefore are not poisonous References https://theconversation.com/handle-with-care-the-worlds-five-deadliest-poisons-56089