In the seventh lecture of the Gnostic Esoteric Astrology course, the zodiacal sign Libra (Sept 23 -  Oct 23) is explained.

Quoted from the lecture:

"Libra is the sign of the balance.  The symbol of Libra is a set of scales.  It is interesting to note that of all of the symbols of the astrological signs, the only one that is mechanical, that is a device, that is not a living thing, are the scales of Libra. "