In Search of Cosmic Order: Selected Essays on Egyptian Archaeoastronomy. Editors: Juan Antonio Belmonte, Mosalam Shaltout. Contributor: Zahi Hawass. Publisher: American University in Cairo Press, 2010. ISBN9789774794834. In chapter 7 on page 197 it says, "The sign held by Seshat over her head has given rise to many attempts to offer an explanation for this rare feature, but none has yielded a definitive conclusion."
Seshat and her tools. H. Peter Aleff. From his article: "Many Egyptologists have long speculated about the emblem which Seshat wore as her head dress. Sir Alan Gardiner described it in his still category-leading 'Egyptian Grammar' as a 'conventionalized flower (?) surmounted by horns'. His question mark after 'flower' reflects the fact that there is no likely flower which resembles this design. Others have called it a 'star surmounted by a bow', but stars in the ancient Egyptian convention had five points, not seven like the image in Seshat's emblem. This number was so important that it caused king Tuthmosis III (1479 to 1425 BCE) to call this goddess Sefkhet-Abwy, or 'She of the seven points'." In the same article Aleff himself describes the figure as "an accurate image of a hemp leaf".
