In 864, Charles the Bald issued what is today known as the Edict of Pistres.
One of his demands was that copies of the standards of measurements (e.g. versions of a foot) were to be displayed on the outside of churches and monasteries. This was the completion of a movement that Charlemagne started 6 decades earlier.
Often these copies were made in stone, directly as part of the buildings. My question is if there are any of these remaining somewhere in France or Germany?