The sack (abbreviation: sck.) was an English unit of weight or mass used for coal and wool.
Contents
Wool
The wool sack or woolsack (Latin: saccus lanae or lane) was standardized as 2 wey of 14 stone each, with each stone 12½ merchants' pounds each (350 lbs. or about 153 kg), by the time of the Assize of Weights and Measures c. 1300. 12 such sacks formed the wool last.
Coal
The coal sack was standardized as an imperial hundredweight of 112 avoirdupois pounds (now exactly 50.80234544 kg).
References
Sack (unit) Wikipedia(Text) CC BY-SA