As mentioned in 'Further Excavations at Mohenjodaro', what seemed to have been the only means in use for grinding cereals for the people of Mohenjodaro in the Harappan period?

Saddle quern

Food processing in the Harappan civilization involved the use of grinding equipment and various vessels for mixing, blending, and cooking.
Stone, metal, and terracotta were the materials used to make these food-processing tools and utensils.
Excavations at Mohenjodaro revealed the presence of saddle querns, which were the primary means of grinding cereals.
Saddle querns were typically made of hard, gritty, igneous rock or sandstone and showed signs of extensive use.