The symbol for prescription -- Rx -- was actually created as an amulet, or an object that worked to ward off evil spirits. It was created in Ancient Egypt. The influence of magic medicine was such that the word for prescription was remedy and also had the meaning of potion or spell.
This is how the Rx came about. Just something interesting I thought I'd share with you.
Prioreschi, Plinio, "A History of Medicine," 1991, vol I, page 345