From Cortés, Second Letter, pp. 158-160

Thus the enemy came off victorious, having regained possession of four of the bridges. The other four I left well guarded, and returned to the garrison, where I constructed a bridge of timer that could be carried by forty men. Seeing the dangerous situation in which we were now placed, and the very serious injury that the Indians were doing us every day; and fearing that they would also destroy the remaining causeway, as they had done the others, and when that was effected death would be our inevitable fate; and moreover, having been often entreated by all my companions to abandon the place, the greater part of whom were so badly wounded as to be disabled from fighting, I determined to quit the city that night. I took all the gold and jewels belonging to your Majesty that could be removed, and placed them in one apartment, where I delivered it in parcels to the officers of your Highness, whom I had designated for the purpose in the royal name; and I begged and desired the alcaldes, regidores, and all the people to aid me in removing and preserving this treasure; I gave up my mare to carry as much as she could bear; and I selected certain Spaniards, as well my own servants as others, to accompany the gold and the mare, and the rest the magistrates above mentioned and myself distributed amongst the Spaniards, to be borne by them. Abandoning the garrison, together with much wealth belonging to your Highness, the Spaniards and myself, I went forth as secretly as possible, taking with me a son and two daughters of Moctezuma and Cacamacin, cacique of Aculuacan, with his brother, who I had appointed in his place, and several other governors of provinces and cities that I had taken prisoners.

Arriving at the bridges, (now broken up,) which the Indians had left, the bridge I carried was thrown over where the first of them had been, without much difficulty, as there was none to offer resistance except some watchmen who were stationed there, and who uttered so loud cries that before we had arrived at the second an immense multitude of enemy assailed us, fighting in every direction, both by land and water.

I sallied across with great speed, followed by five horsemen and a hundred foot[soldiers], with whom I passed all the (broken) bridges swimming, and reached the main land. Leaving the people who formed this advanced party, I returned to the rear, where I found troops hotly engaged; it is incalculable how much our people suffered, as well Spaniards as our Indian allies of Tascaltecal, nearly all of whom perished, together with many native Spaniards and horses, besides the loss of all the gold, jewels, cotton cloth, and many other things we had brought away including the artillery. Having collected all that were alive, I sent them on before, while with three or four horse[s] and about twenty foot[soldiers] that dared to remain with me, I followed in the rear, incessantly engaged with the Indians, until we at length reached a city called Tacuba, [Tlacopan,] beyond the causeway, after encountering a degree of toil and danger, the extent of which God only knows.

[Cortés estimated that he lost 150 Spaniards, forty-five horses, and 2000 Indian allies including Moctezuma's son and daughter in the battle.]