Arrian, Anabasis 3.1.5-2.2
When he (Alexander) had reached Canobus and sailed round Lake Mareotis, he went ashore where the city of Alexandria, named after him, is now situated. It struck him that the position was admirable for founding a city there and that it would prosper. A longing for the work therefore seized him, he himself marked out where the city's marketplace was to be built, how many temples there were to be and the gods, some Greek, and Isis the Egyptian, for whom they were to be erected, and where the wall was to be built round it. With this in view he offered sacrifice, and the sacrifice proved favorable.
 A story of the following sort is told, and personally I do not disbelieve it; Alexander desired to leave the builders outlines of the fortification, but had no means of marking the ground. One of the builders, however, had the happy thought of collecting the meal which the soldiers carried in vessels, and of dropping it on the ground wherever the king indicated. In this way was the circle of the surrounding wall which he proposed to make for the city marked out. (2) The soothsayers, and especially Aristander the Telmissian, who was reported to have made many other correct prophecies to Alexander, reflecting upon this, said that the city would be prosperous in general, but particularly in the fruits of the earth.