Sentence:  The American <WSD>sack</WSD> of salt is 215 pounds; the <WSD>sack</WSD> of wheat, two bushels. 
Meaning of the word marked with <WSD> tags:  The amount a sack holds; also, an archaic or historical measure of varying capacity, depending on commodity type and according to local usage; an old English measure of weight, usually of wool, equal to 13 stone (182 pounds), or in other sources, 26 stone (364 pounds).