The London Staple System
Designated ports, fixed measures, and a Crown that took its cut of everything.
Origin
Formalised by the Ordinance of the Staple in 1353 and the Statute of the Staple in 1354, under Edward III.
The catch
The staple was not a measurement system so much as a monopoly enforced by measurement. Certain goods could be exported only through designated towns, where they were weighed, graded and taxed under royal supervision. Standard measures existed because the Crown needed them to collect.
The principal staple commodity, taxed by the sack of 364 pounds. Export duty on wool funded much of the Hundred Years War.
Sheepskins with the fleece still attached, counted in long hundreds of 120.
Ten hides to a dicker, twenty dickers to a last: 200 hides in all.
Roughly a ton, though the fother varied by region and required its own local standard.
Cornish tin was assayed and stamped at coinage towns before it could legally be sold.
The staple towns shifted with politics: Calais held the wool staple for well over a century, which made an English possession in France a central institution of English commerce. The word survives in the modern sense of a staple good, meaning something basic and reliably traded, which is a considerable softening of what was originally a tightly policed royal monopoly.