During the Middle Ages, European measurement standards went from diverse, local and confusing, to something like “national though still confusing.” Originally, each trade in each city policed measurements, so not only did the sizes vary from place to place, but also from trade to trade. The joke about which is heavier, a pound of feathers or a pound of lead, would not raise a laugh in a medieval town. They’d just wonder—because the metal workers and feather-pillow-stuffers probably did use different “pounds.”
One early medieval measurement was something around a hundred pounds, and it was called a “centner” (notice the root for “hundred,” from Latin centum). But a centner of wax was not equal to a centner of food, silk, yarn, lard, or lead. 12th-century Paris had two official royal scales: one was used only for wax, for which all of the weights were different.
The Magna Carta was signed into English law around this period, and it noted that the realm needed to adopt national weights and measures. Local ones allowed merchants to cheat too easily because it was hard for a traveler to understand the local measurements. It was impossible to have an agreement that was binding for the whole nation when words meant different things. As late as 1340, the king was still trying to reform the weights and measures system by sending in new (identical) sets of weights to each county.
Local enforcement was done by guild, and since the guilds elected the mayor (he was the Major–the leader–of the guild chiefs), from the mayor’s office. The mayor kept a set of weights and measures that were official for that time–by 1340, obviously they had to match the royal ones. But someone needed to keep a log book of how many guilds and merchants had verified their weights with the mayor’s set. In London, this job typically went to the widow of a town official. The widow could keep the weights in her home as a genteel way to support her family (she charged certification fees to each merchant or guild).
Early, primitive weights in places like Scandinavia were made of iron and shaped like something cool, such as a lion. Later, royal weights were still made of iron most of the time, but they came in standard shapes like cubes or bells. They had to be marked by the blacksmith who cast them, and they had to include a ring on top, in case they needed to hang from a hook. Eventually weights shifted to brass, which was cheaper. Discount-quality weights were made of lead–the cheapest metal, but soft enough to pare away with a knife without anyone noticing.
Each merchant had his own set of weights; it was part of the cost of doing business. With a balance on hand, he could measure out portions and then hand them to the buyer, who put them into his own containers. Buyers usually watched to see if the merchant left his hand near the balance pan that held bread, meat or wax. He might be using sleight of hand, like a magician, to distract the buyer while he held the balance pan down to an inaccurate weight. Buyers could watch for this kind of trick, but they could not make sure the weights themselves were not wrong. On the other hand, some buyers turned out to be undercover town officials, so merchants were hard pressed to cheat openly.
Merchants who sold underweight goods were fined heavily. When their goods were edible, like under-sized loaves of bread or shrunken casks of wine, the confiscated wares became jail food. In later times especially, towns went a step farther, shaming dishonest merchants in public pillories.
A town’s reputation rested on how well its government policed weights. This was fair, since the town government was usually directly elected by the craft guilds, and the craft guilds could decide how much it mattered to them if the town had a bad reputation. If they wanted more policing, they could tax themselves more for increased supervision. Most guilds took a hand in the process on their own, too.
next: kinds of weights and balances