Final answer:
A historian could look to Aztec codices, accounts written by Spanish conquistadors, archaeological findings, and the observations of Spanish priests to discover the religious beliefs of the Aztecs.
Step-by-step explanation:
A historian could look to various sources to discover the religious beliefs of the Aztecs. Some of these sources include Aztec codices, accounts written by Spanish conquistadors, archaeological findings, and the observations of Spanish priests who accompanied the conquistadors. For example, the Florentine Codex, written in the 16th century, is a valuable source that provides detailed information on Aztec religious practices and beliefs.
Learn more about Aztec religious beliefs