Abracadabra is known in the modern world as an incantation used as a magic word in stage magic tricks. However its history can be traced back to that of its apparent power in the healing disease and infection. Deriving possibly from the Aramaic phrase "I create as I speak”, its first use as an healing amulet is mentioned in Liber Medicinalis, or De Medicina Praecepta Saluberrima, composed between 350 and 300 AD. Written by Quintus Serenus Sammonicus (died 212 AD) physician to the Roman emperor Antoninus ‘Caracalla’ (4 April 188 – 8 April 217), the book speaks of malaria sufferers being cured by the wearing an amulet containing the word Abracadabra written in the form of a triangle. By the time of the Great Plaque of London (1665–66) it was still in use as a healing amulet, Daniel Defoe in his account of the plaque writes dismissively about Londoners who posted the word on their doorways to ward off sickness.