Wikipedia:
On April 21, 1787, the Congress of the Confederation of the United States authorized a design for an official copper penny, later referred to as the Fugio cent because of its image of the Sun and its light shining down on a sundial with the caption, "Fugio" (Latin: I flee/fly). This coin was reportedly designed by Benjamin Franklin; as a reminder to its holders, he put at its bottom the message, "Mind Your Business." This design was based on the "Continental dollar" coin, which was never circulated.*Previously: Stephen Hawking UK 50p Coin.
Some historians believe that the word "business" was intended literally here, as Franklin was an influential and successful businessman. It does not mean "mind your own business" as that phrase is used today, but rather, "pay attention to your affairs."