Food historian Rachel Ludan has a really interesting article on how tedious milling grain (especially maize) used to be, particularly for women.

To me this again goes to show how laborious life was in the past, and how thankful we should be for the industrial revolution:

Quite how long it takes a woman to grind for a family, apart from the time husking and shucking the maize, collecting the cooking water, and shaping and cooking the tortillas, depends on her skill and strength, the age and number of family members, the type of masa, and the quality of the metate. My estimate is that it takes about five hours a day to make enough masa for a family of five. [...]  Since five hours is about as much as anyone can grind, the labor of one in five adults has to be devoted to making the staple bread.