From Cortés, Second Letter, 76–77

As I have desired to render your Highness a very minute account of every thing in this part of the world, I wished to ascertain the cause of this phenomenon [smoke coming from a snow-capped mountain], as it appeared to me, and I dispatched ten of my companions, such as I thought suitable for this, purpose, with several natives of the country for guides, charging them to use every endeavor to ascend the mountain and find out the cause of that smoke, whence and how it was produced. They went, and struggled with all their might to reach the summit, but were unable on account of the great quantity of snow that lay on the mountain, and the whirlwinds of ashes that swept over it, and also because they found, the cold above insupportable; but they reached very near the summit, and while they were there, the smoke began to issue forth with so much force and noise that it seemed as if the whole Sierra was crumbling to the ground. so they descended, and brought with them a considerable quantity of snow and icicles, that we might see them, as, it was something quite new in this region on, account of its being in so warm a latitude, according to the opinion, of our pilots, who place it in. 20^o, which is the same parallel as the Island of Española, where the heat is at all times extreme. While on their way to the mountain, the party discovered a road, and inquired of their Indian companions where it led, who told them to Culua, [Mexico,] and that it was a good road, while the other, which the Culuans wished us to take, was not a good one. The Spaniards followed this road until they began to ascend the mountain, between which and the other elevation it passed; and from it they discovered the plains of Culua, and the great city of Tenochtitlan, [Mexico,] and the lakes in that province, of which shall hereafter give your Highness an account; they returned overjoyed on having discovered so good a road, and God knows how much joy I felt on the occasion. Havng obtained all the information I could from the Spaniards who had returned from their visit to the mountain, as well as from the natives, concerning the road they had discovered, I addressed myself to the envoys of Moctezuma, who accompanied me as guides to their country and said to them, that I would take the new route instead of that which they; had recommended, as it was, shorter. They answered that I was right, that the new route was shorter and more level, and that the reason they had not pointed it out to me was, that we should have to pass one day through the territory of Guasucingo, [Guajozingo,] whose inhabitants were their enemies, and would not furnish supplies, as was done in the territory of Moctezuma; but that since I preferred that route, they would cause provisions to be sent in that direction. And thus we set forth, not without some apprehension that they would persist in their endeavors to entrap us; but as we had already declared what route it was our intention to take, it did not seem to me worth while to change our plan, or to return on our steps, lest they should imagine that our courage failed us. On the day that I left the city of Cholula, I advanced four leagues to some villages in the state of Guasucingo, where we were well received by the natives, who gave me a number of female slaves, some cotton cloth, and several small pieces of gold . . . .