Αλεξανδρου αναβασις 5.8.5

5.8.5

καὶ ξυνετμήθη τε τὰ πλοῖα καὶ ἐκομίσθη αὐτῷ, ὅσα μὲν βραχύτερα διχῇ διατμηθέντα, αἱ τριακόντοροι δὲ τριχῇ ἐτμήθησαν, καὶ τὰ τμήματα ἐπὶ ζευγῶν διεκομίσθη ἔστε ἐπὶ τὴν ὄχθην τοῦ Ὑδάσπου κἀκεῖ ξυμπηχθέντα ναυτικὸν αὖθις δὴ ὁμοῦ ὤφθη ἐν τῷ Ὑδάσπῃ. αὐτὸς δὲ ἀναλαβὼν ἥν τε δύναμιν ἔχων ἧκεν ἐς Τάξιλα καὶ πεντακισχιλίους τῶν Ἰνδῶν, οὓς Ταξίλης τε καὶ οἱ ταύτῃ ὕπαρχοι ἦγον, ᾔει ὡς ἐπὶ τὸν Ὑδάσπην ποταμόν.

This method has been practised by the Romans from of old, but how Alexander bridged the river Indus I cannot say, for even those who served in his army are silent on the matter. But the bridge was made, I should think, as nearly as possible in the way described, or if it was otherwise contrived let it be so.
When Alexander had crossed to the other side of the Indus he again offered sacrifice according to his custom. Then marching away from the Indus he arrived at Taxila, a great and flourishing city, the greatest indeed of all the cities which lay between the river Indus and the Hydaspes. Taxiles, the governor of the city, and the Indians who belonged to it received him in a friendly manner, and he therefore added as much of the adjacent country to their territory as they requested. While he was there Abisares, the king of the Indians of the hill-country, sent him an embassy which included his own brother and other grandees of his court. Envoys came also from Doxares, the chief of the province, and these like the others brought presents. Here again in Taxila Alexander offered his customary sacrifices and celebrated a gymnastic and equestrian contest. Having appointed Philip, the son of Makhatas, satrap of the Indians of that district, he left a garrison in Taxila and those soldiers who were invalided, and then moved on towards the river Hydaspes — for he had learned that Poros with the whole of his army lay on the other side of that river resolved either to prevent him from making the passage or to attack him when crossing.
Upon learning this Alexander sent back Koinos, the son of Polemokrates, to the river Indus with orders to cut in pieces all the boats that had been constructed for the passage of the Indus and to bring them to the river Hydaspes. In accordance with these orders the smaller boats were cut each into two sections and the thirty-oared galleys into three, and the sections were then transported on waggons to the banks of the Hydaspes. There the boats were reconstructed, and appeared as a flotilla upon that river. Alexander then taking the forces which he had with him when he arrived at Taxila and 5000 of the Indians commanded by Taxiles and the chiefs of that country advanced towards the Hydaspes.