Ounceland - it is based on the rent paid, rather than the actual land area

From Ounceland in Wikipedia

An ounceland (Scottish Gaelic: unga) is a traditional Scottish land measurement. It was found in the West Highlands, and Hebrides. In Eastern Scotland, other measuring systems were used instead. It was equivalent to 20 pennylands or one eighth of a markland. Like those measurements, it is based on the rent paid, rather than the actual land area. It was also known as a "tirung" (from Scottish Gaelic: tìr-unga), or a dabhach (same as daugh), which is a term of Pictish origin, also used in the east of Scotland too, but for a different measurement. The “ounceland” is thought to be of Norse origin, so it is possible that Norse (‘ounceland’) and native systems (dabhach) were conflated in the west.