Carl Nebel, Las Tortilleras

"It was the woman's task to spend four or five hours a day on her knees grinding corn on the metate, similar to the concave grinding stone in ancient Egypt, and one of the oldest domestic tools in the Americas. She placed a small amount of prepared corn kernels on the metate, leaned over, and rolled the mano back and forth- three passes for a skilled grinder to partially grind for a corn drink. She repeated the sequence until she was satisfied with the mixture to make tortillas and tamales. It was hard work bending and grinding, and in time she rubbed the palm of her hands raw, and the joints of her fingers ached." Tortillas: A Cultural History, Paula E. Morton 

Prototype Testing 02 by Ing. Piña from Celorio Tortilla Machines