Before metrication it was used alongside the morgen and many other agrarian units.
I heard somewhere (it might have been here) about measuring by working time.
This could vary by region, by worker and by difficulty of the work. I think
the furlong was one such units (i.e. the length of a furrow). Given the
nature of agriculture hundreds of years ago (feudal obligations and limited
alternative ways of measurement), it makes a lot of sense to look at the
world that way. I remember something about a dispute over the working day in
rural parts of France and in the cities.
The furlong was the length of the furrow that could be plowed with a team of oxen before lunch time. After eating his lunch, the plowman turned around and plowed his way back to the edge of the field. I remember that my father also called it an *acre*. The acre was supposed to be the area that a team of oxen could plow in a day. The Prussian and Dutch "Morgen" (meaning morning) may have had a similar meaning to the English acre. The Prussian Morgen was 2532 m2 and the Dutch morgen was 8244 m2.
In mountainous Switzerland distances were expressed in "Stunden" (hours), which was the time it would take a man to walk between two points.
