The caravan of merchants wandering out of the direct way had a certaine blinde man in their companie which was acquainted with all those regions: this blinde guide riding foremost upon his camell, commanded some sand to be given him at every miles end, by the smell whereof he declared the place, but when they were come within fortie miles of this region, the blinde man smelling of the sand, affirmed that they were not farre from some places inhabited which some beleeved not, for they knew that they were distant from Egypt fower hundred and eightie miles.
-Description of Africa, Book VII, Leo Africanus (1494-1554), trans. John Pory, 1600
This is one of those old Saharan tall tales, that Khabīrs knew where they were by the smell of the sand. Maybe the story originated with Leo the African and European travellers after him repeated it to the point of making a commonplace. KhairAllah never pulled it on me but he did say how the feel of the wind on his left cheek told him to keep going straight, and thereby we did get to Cairo.