Ptolemy, Pliny the Elder, De architectura, and it appears on the Antonine Itinerary. It also is mentioned in the Book of Ezekiel and the Book of Isaiah.
The latitude of the city that would become Aswan – located at 24° 5′ 23″ – was an object of great interest to the ancient geographers. They believed that it was seated immediately under the tropic, and that on the day of the summer solstice, a vertical staff cast no shadow. They noted that the sun's disc was reflected in a well at noon. This statement is only approximately correct; at the summer solstice, the shadow was only 1/400th of the staff, and so could scarcely be discerned, and the northern limb of the Sun's disc would be nearly vertical.
Eratosthenes used measurements at Aswan (Elephantine) to determine the circumference of Earth, using Syene as the originating point and Alexandria as the terminal point of a measured arc (based on shadow length at the solstice).
The Nile is nearly 3,000 yards wide above Aswan. From this frontier town to the northern extremity of Egypt, the river flows for more than 750 miles (1,210 km) without bar or cataract. The voyage from Aswan to Alexandria usually took 21 to 28 days in favourable weather
