A brief reference, without explanation, to a person, text, myth, or fact known outside the work, which brings with it the meaning of that other story.
In Don Quixote
sister, if the same spirit and courage you showed in defending this purse were shown, and even half as much, in defending your body, the strength of Hercules would not be enough to force you.
Hercules, the hero of proverbial strength, sets the measure of what it would take to overcome the woman, and the mention gives the governor's argument the weight of a famous verdict.
Part Two: The Governorship of the Island, Sancho as governor, to the woman who accused a pig breeder