The pietre di paragone got the same treatment, with units of length carved as stone incisions into the walls of churches and markets. Officials could then check their standards by inserting them into these spaces. Using these hollows to verify units was a simple and clever way to avoid tampering, as they could not be shortened and lengthening could be stopped with the use of metal end caps. As Lugli notes: ‘While an object can be manipulated, a void is incorruptible.’
