Stone is a fun one. The singular and the plural are the same, like deer. So 1 stone is correct and 2 stone is also correct.

For livestock, there was a pre-butcher (14-pound) and a post-butcher (8-pound) value for stone.

A customer brings a lamb in that is very much alive and that weighs, say, 8 stone.

The blood, hide, and offal is kept by the butcher. After that's subtracted, about 8 stone of meat and bone is expected to be returned to the customer.

Acre itself is fun, too: That's about how much land one man with one ox can plow in one workday. It was a convenient way to keep farmland in perspective.

Anyway, an acre-foot of water weighs a little bit shy of 200,000 stone.

It takes very close to 2 acre-feet of water to fill one olympic-sized swimming pool.

> the term hogshead fell out of use after The Netherlands converted to the metric system in 1816

Do you have a slightly more recent example?