This paper examines the use of mathematical symmetry in the stylized depiction of the date-palm on the sculptured stone wall reliefs decorating the royal palace of the Assyrian king, Ashurnasirpal II in the 9th century BC. Although the significance of the date palm in Neo-Assyrian iconography is still debated, the frequency of its appearance on the palace walls indicates that it played an important role in Assyrian apotropaic ritual. We argue that one of the keys to unlocking the mystery of the ritual is to understand the principles underlying the formal depiction of the date palm.