National Geographic : 1922 Nov
UNCHANGED BY THE PASSING OF FiOUR CENTURIES Throughout Mexico the threshing of the wheat by natives is done in this way, just as it is done in Spain and Arabia to-day. The wheat stalks are scattered upon the stones of the threshing-floor, and then mules are driven upon it. Sometimes they drag aheavy weight, which constitutes the most modern improvement known to the majority of threshing crews in Mexico. After some hours the strawisraked away, the wheat swept into piles, and then a peon winnows it in the manner shown in the picture. The wind blows away the lighter chaff.