https://www.laphamsquarterly.org/roundtable/how-much-smidgen
The beauty of the stone as a unit of measure was that any locality could identify a rock of decent dimensions and adopt it as the local stone in weight. Since antiquity a stone had been used as a measure, although it did not need to be assigned an actual value. Instead, any good-sized stone could be used as a counterbalance to ensure that commodities could be equally split, meaning that this system could be used in societies where arithmetic had yet to develop. Across northern Europe stones were used in this way to measure dry goods, with the earliest examples dating back to the Roman Empire. (The pound of weight also originates in the Roman Empire, where it was known as libra pondo. It derived from the Latin word libra, which like the sign of the zodiac meant a balance or scale but was also used to refer to a measure—pound by weight. This Latin word is the reason why pounds are abbreviated as lbs.—a shortening of the word libra. There was little standardization, and the weight of stones could vary from country to country, region to region and even village to village, ranging from as little as 4 lbs. all the way up to 40 lbs. It was not only the location which affected the weight of the stone; sometimes the weight varied depending on the goods being weighed. For example, an English statute from around 1300 set a London stone at 12.5 lbs.; however, a stone for weighing lead was said to be 12 lbs., while a stone for measuring beeswax, sugar, pepper, cumin, almonds and alum was 8 lbs., and the stone for weighing glass was 5 lbs. The inconsistent and archaic use of stones continued in Britain for some time. An example of this can be seen in the system used by British butchers: the stone used for measuring the weight of livestock was generally accepted to be 14 lbs. but the resultant meat was measured with an 8 lbs. stone. It is thought that this was because butchers would return the dressed meat from an animal carcass back to the farmer stone for stone—the weight difference meant that the butcher could keep the blood, offal and hide as payment. Butchers at Smithfield Meat Market in London continued to employ the 8 lbs. stone right up until World War II.
