The sistrum is an instrument used by the Romans (and others) in the worship of Isis, shaken like a rattle. I drew Iusta's with three bars, but it is also depicted with four, and usually with a looped top reminiscent of an ankh, but there are variations on the design. The sound of the sistrum attracts the attention of the gods, placates them, and drives away malicious creatures. Egyptians in earlier times associated the instrument with the goddess Hathor before also assigning it to Isis. Some sources say the sistrum might have evolved from shaking bundles of papyrus flowers—an origin explanation I quite like.
