White arsenic, the poison used at the Shelbourne, was a favorite of some of history’s most feared poisoners, ones who made Jean Crones look like the amateur he was. At the top of the list were Lucretia and Cesare Borgia, feared in fifteenth-century Italy for their ruthless mixture of politics and poison. The Borgias used white arsenic preferentially but experimented with different ways to make it more deadly.
