King Edgar’s standards

We live, profit and die by our units. They are the firm ground on which everyone can stand, and the ones we learn as children stay with us to our dying day. Once, on a trip to France, I stopped in the small town of Laon, one of the great centres of medieval scholarship. Passing the gateway of the ruined town hall, three cast iron objects embedded in the wall caught my eye. Two were the standard templates for roof tiles and bricks; the third was a long iron rod. At one end of the rod, two humps denoted the limits of the Parisian pied (foot), itself divided into twelve pouces (thumbs or inches). A final mark close to the top denoted the length of three pieds, not far from the metre length that would be adopted when Napoleon reformed measurement in France.