How many furrows can a horse make in a day

A wonderful article on mensuration in (I believe) Model Engineer
or Model Engineers Workshop a few years ago, by Tubal Cain
(sadly, now deceased) explained the origins of many of today's
and past standard measures.

He pronounced that the Pilgrims were wine drinkers, based on the
size of the gallon jugs (132 oz) they brought with them; a gallon
of beer comprised 160 oz. - this is, he claimed, the origin of the
US gallon...... A "real" gallon (Imperial) is, of course, 160.

The furlong, I think, was the length of furrow a horse pulling a single
plowshear could make in a day. My memory could be faulty, but
the article is definitely worth a read.... /mark