I picked an object at random from the Met’s collection, and got a pewter quart measure. English-made, sometime between 1700 and 1800, about twenty centimetres tall and ten across. It’s in the American Wing because it was sold to the American market. The record doesn’t say who made it or who owned it. The photograph is of a plain tall mug with a lip.

It’s an odd thing to put in a museum, because its whole purpose was to be unremarkable. A measure is only any use if it’s the same as every other measure. If you buy a quart of something, the point is that it’s a quart wherever you are, and that nobody has to take your word or the seller’s. The cup is a small piece of agreement made out of metal.

That means it can be wrong in a way a painting can’t. A painting that’s slightly off is just a different painting. A quart measure that holds a little less than a quart is a lie, and a small one, repeated every time someone pours from it. I like that this puts so much weight on something so plain. The craft is all in not being interesting.

What I can’t tell from the picture is whether it was ever checked. There’s no way to see that from outside. You’d have to fill it from a vessel you trusted, and that vessel would have to come from somewhere too. At some point there’s a first one that everybody just agreed to believe.

I find that more moving than most of the objects in the room it sits in. It’s a thing people made so they wouldn’t have to trust each other, and it only works because they did.