والوسق ستون صاعا بصاع النبي صلى الله عليه وسلم
Translation: One wasq consists of sixty saʿ measured by the Prophetic saʿ.
A wasq is a classical capacity measure, defined here in units of the saʿ: 1 wasq = 60 saʿ.
The Prophetic saʿ is the reference measure. A precise modern kilogram equivalent should not be asserted here without settling the relevant historical measurement conventions.