Grain of salt


To take something with a "grain of salt" or "pinch of salt" is an English language idiom that means to view something with skepticism or not to interpret something literally.
In the old-fashioned English units of weight, a grain weighs approximately 60 mg, which is about how much table salt a person might pick up between the fingers as a pinch.

History

Hypotheses of the phrase's origin include Pliny the Elder's Naturalis Historia, regarding the discovery of a recipe for an antidote to a poison. In the antidote, one of the ingredients was a grain of salt. Threats involving the poison were thus to be taken "with a grain of salt", and therefore less seriously.
The phrase cum grano salis is not what Pliny wrote. It is constructed according to the grammar of modern European languages rather than Classical Latin. Pliny's actual words were addito salis grano.
An alternative account says that the Roman general Pompey believed he could make himself immune to poison by ingesting small amounts of various poisons, and he took this treatment with a grain of salt to help him swallow the poison. In this version, the salt is not the antidote. It was taken merely to assist in swallowing the poison.
The Latin word sal means both "salt" and "wit", thus the Latin phrase "cum grano salis" could be translated to either "with a grain of salt" or "with a grain of wit", actually to "with caution"/cautiously.
The phrase is said "with a pinch of salt" in British English and said "with a grain of salt" in American English.