Jones, Alexander. Astronomical papyri from Oxyrhynchus. 1999. ISBN 0-87169-233-3. с. 62 – 63. It is now possible to trace the medieval symbols for at least four of the five planets to forms that occur in some of the latest papyrus horoscopes ([ P.Oxy. ] 4272, 4274, 4275 [...]). Mercury's is a stylized caduceus. … The ideal form of Mars' symbol is uncertain, and perhaps not related to the later circle with an arrow through it.
