From Cortés, First Letter

Everyday, before they undertake any work, they burn incense in the said mosques [temples] and sometimes they sacrifice their own persons, some hacking the body with knives; and they offer up to their idols all the blood which flows, sprinkling it on all sides of those mosques, at other times throwing it up towards the heavens, and practicing many other kinds of ceremonies, so that they undertake nothing without first offering sacrifice there.

They have another custom, horrible, and abominable, and deserving punishment, and which we have never before seen in any other place, and it is this, that, as often as they have anything to ask of their idols, in order that their petition may be more acceptable, they take many boys or girls, and even grown men and women, and in the presence of those idols they open their breasts, while they are alive, and take out the hearts and entrails, and burn the said entrails and hearts before the idols, offering that smoke in sacrifice to them. Some of us who have seen this say that it is the most terrible and frightful thing to behold that has ever been seen. So frequently, and so often do these Indians do this, according to our information, and partly by what we have seen in the short time we are in this country, that no year passes in which they do not kill and sacrifice fifty souls in each mosque; and this is practiced, and held as customary, from the Isle of Cozumel to the country in which we are now settled. Your Majesties may rest assured that, according to the size of the land, which to us seems very considerable, and the many mosques which they have, there is no year, as far as we have until now discovered and seen, when they do not kill and sacrifice in this manner some three or four thousand souls. Now let Your Royal Highnesses consider if they ought not to prevent so great an evil and crime, and certainly God, Our Lord, will be well pleased, if, through the command of Your Royal Highnesses, these peoples should be initiated and instructed in our Very Holy Catholic Faith . . . .