Mescal, the heart or piña of the agave plant (see bookmark p.155 'they rode through strange forests of maguey'), was cultivated and treasured as a valuable source of food, fibre and medicine for many Indian tribes of the Southwest, including the Havasupais, Hopis, Yavapais, Maricopas, Papagos, Walapais, Kaibabs, and the White Mountain, Chiricahua, and Mescalero Apaches.
Although toxic when raw, burning the mouth, mescal (the heart of the agave) was edible when roasted. The Indians dug huge roasting pits in the fields, ten to twelve feet in diameter, three to four feet deep, lined with large flat rocks; a mound of oak or juniper wood was placed in the bottom and the fire ignited before dawn. By noon, it had died down and moist grass was laid on the stones. Between one and three dozen agave crowns were roasted together, each surrounded by a mound of rocks to hold moisture in the ground. The pit was covered with bear grass, a tall western plant used to make baskets, and then a thick layer of earth and allowed to roast for two days. After the crowns cooled, the center portion or heart was eaten or dried in the sun. As agave was harvested before the plant produced its flower, it contained a large store of carbohydrates that converted to a sugary, highly nutritious food. Each heart furnished about 347 calories, 4.5 grams of protein per 100 grams weight and more calcium than a glass of milk.
(Linda Murray Berzok, American Indian Food)