Titus Livius (Livy), The History of Rome, Book 21
Benjamin Oliver Foster, Ph.D., Ed.

28. The Gauls rushed to meet them on the bank, with all sorts of yells and their customary songs, clashing their shields together above their heads and brandishing darts in their [2??] right hands, despite the menace of so great a multitude of vessels coming against them and the loud roaring of the river and the confused hallooing of the boatmen and the sailors, as they strove to force their way athwart the current or shouted encouragement to their fellows [p. 81]from the further bank. [3] But the tribesmen were already¹ somewhat daunted by the tumult which confronted them, when a still more appalling clamour arose in the rear, where Hanno had captured their camp. He was soon on the scene himself, and a twofold terror hemmed them in, as that mighty force of armed men came out upon the shore and the unlooked-for line of battle closed in from behind. [4] When the Gauls had attempted charges in both directions and found themselves repulsed, they broke through where the way seemed least beset, and fled in confusion to their several villages. Hannibal brought over at leisure the rest of his forces, and giving himself no more concern over Gallic outbreaks, pitched his camp.

I believe that there were various plans for transporting the elephants; at all events the tradition varies as to how it was accomplished. [5] Some say that the elephants were first assembled on the bank, and then the keeper of the fiercest of them provoked the beast and fled into the water; as he swam off, the elephant pursued him and drew the herd in his train; and though they were afraid of the deep water, yet as soon as each of them got out of his depth, the current itself swept him over to the other bank. [6] It is, however, more generally believed that they were carried across on rafts; this method, as it would be the safer, if the thing were to be done, so, in view of its accomplishment, is more probably the one employed. [7] A raft, two hundred feet long and fifty feet wide, was thrust out from the shore into the stream, and, after being moored to the bank above by a number of stout hawsers, so as not to be carried down the current, was covered with earth, [p. 83]like a bridge, in order that the beasts might boldly² venture upon it, as on solid ground. [8] A second raft, of equal width and a hundred feet long, and fit for crossing the river, was coupled to the first. Then the elephants, with the females leading, were driven out over the stationary raft, as over a road; and after they had passed on to the smaller raft adjoining it, the ropes by which this had been loosely attached were cast off and it was towed across by some rowboats to the eastern bank. [9] After landing the first contingent in this fashion, they returned and fetched the others over. [10] The elephants exhibited no signs of fear so long as they were being driven along as though on a connected bridge; they first became frightened when the raft was cast loose from the other and was carried out into mid-channel. [11] The crowding together which resulted, as those on the outside shrank back from the water, gave rise to a slight panic, till terror itself, as they looked at the water all about them, made them quiet. [12] Some, in their frenzy, even fell overboard; but, steadied by their very weight, threw off their riders, and feeling their way to the shallow places, got out upon the land.³