Beans (frijoles) — the complementary protein to corn in the Mesoamerican diet — have been cultivated in Mexico for at least 7,000 years. The Mexican tradition of cooking beans in a clay pot (olla de barro) from cold water with epazote is the foundational legume technique of the Americas, and the technical reasons for each element (cold start, clay pot, epazote, no salt until done) are documented in Mexican culinary sources.
The complete frijoles de olla technique.
MEXICAN CULINARY TRADITION — DEEP EXTRACTION