I read a bridge column by Frank Stewart in the Denver Post on June 11, 2012 that “King Mithridates VI of what is now Turkey was always trying to avoid assassination. He took food with a concoction that included a grain of salt, believing it to be a poison antidote. Hence, taking something ‘with a grain of salt’ – with caution. The Phrase Finder adds that the expression means that a statement can be accepted but with “…a degree of skepticism about its truth.” For those who want to replicate the antidote, the grain of salt was added to two dried walnuts, two figs, and twenty leaves of rue that were pounded together.