Pompey the Great (106-48 B.C.) found in the palace of his deceased friend, Mithridates (mith-ri-DAY-teez), an antidote against poison--the ancient antecedent of "gun control"--which was, according to historian Pliny (PLIH-nee;23-79 A.D.), to be taken on an empty stomach with but a single grain of salt, presumably to counteract the bad taste of the antidote.
Sometime during the past two millennia, the expression "cum grano salis" has come to mean that one accepts an observation or a statement with a little reservation or skepticism.