Bag (unit)

Bags have been used as standard measures for a variety of commodities which were actually supplied in bags or sacks. These include:

Cement is commonly sold in bags of 94 pounds weight, because this is about 1 cubic foot of powdered cement.
Agricultural produce in England was sold in bags which varied in capacity depending on the place and the commodity. Examples include:
Bags are used as units by the National Agricultural Statistics Service of the United States Department of Agriculture for the following commodities:

The Oxford English Dictionary has a definition of "bag" as "A measure of quantity for produce, varying according to the nature of the commodity" and has quotations illustrating its use for hops in 1679, almonds in 1728 and potatoes in 1845.