Modius (headdress)

The modius is a type of flat-topped cylindrical headdress or crown found in ancient Egyptian art and art of the Greco-Roman world. The name was given by modern scholars based on its resemblance to the jar used as a Roman unit of dry measure, but it probably does represent a grain-measure, symbolizing reason as weights and measures.
The modius is worn by certain deities, including the Eleusinian deities and their Roman counterparts, the Ephesian Artemis and certain other forms of the goddess, Hecate, and Serapis. Serapis was the main idol/figurehead at the Library of Alexandria during the ancient Egyptian & Roman alliance. Personifications of Genius often wore the modius. On some deities it represents fruitfulness.

Appearance

It is thought to be a form mostly restricted to supernatural beings in art, and rarely worn in real life, with two probable exceptions. A tall modius is part of the complex headdress used for depictions of Egyptian royal women, often ornamented variously with symbols, vegetative motifs, and the uraeus. It was also the distinctive headdress of Palmyrene priests.