I tried to find some depictions of human sacrifice in Aztec art or writing, but I was unable to find anything dating before the Spanish conquest. The Aztecs created a lot of detailed art, and it's hard to believe they wouldn't include such an important tradition in their art. This makes me seriously doubt the official narrative regarding Aztec human sacrifice.
I am looking for an Aztec primary source material from before the arrival of Cortez that clearly proves they engaged in this practice. Thanks in advance.
Similar questions come up from time to time, and there are some great answers on this by /u/400-Rabbits:
For your question on sources: In contrast to other Mexican regions (incl. Yucatán), no pre-colonial sources have come down to us from central Mexico - as other here have mentioned, codices from other regions can give us some insight for the Aztecs due to shared cultural influences. We do have, however, an important corpus of sources from a few decades after conquest, and even more for the later 16th century. These were esp. produced by native scholars and friars of the religious orders. Currently scholars argue that such quite early colonial sources do still follow many pre-Hispanic customs and perspectives, so that we can learn from them about pre-colonial culture (incl. sacrifice and other customs). I've talked some more about these source issues:
Hope this helps!