The Libra constellation was based on the Scales carried by the Goddess of Justice and Purity, Astræa. When she ascended to the Heavens, and became a constellation, her scales became the nearby constellation Libra. The constellation could be used to symbolize the balance of good and evil, or the weighing of both sides of the argument in a trial, to see which one holds true.

The constellation also has a connection to Egyptian mythology, as it symbolized a special scale found in the Underworld; when a person died, they had to journey until they came to a special hall for judgment. The dead person's heart was set on one plate of a scale, while a feather, the Feather of Truth, was placed on the other. If the heart proved lighter than the feather, the soul was deemed worthy to travel on to the utopian Underworld. If not, it was devoured by a monster and the soul ceased to exist.