Carelli&#39s proposed digital standardOne of the most well-known and much-loved units of length in the metric system, the centimetre was first proposed simultaneously in 1710 by Italian mathematician Luciano Carelli and Norwegian physicist Bernhard Boger. A bitter authorship debate ensued, with the central issue being the question of which physical phenomenon should be used as the basis of measurement. Carelli was adamant that a centimetre should be defined as “the width of the smallest finger on my leftmost hand, at the point directly between the finger nail and the upper knuckle”, but Boger dismissed this idea as absurd, arguing that the width of Carelli’s fingers was liable to change if he were to put on excessive weight, or to die and slowly decay. He instead proposed that a much more reliable definition would be the size of the gap between his writing desk and the wall of his study, pointing out that the construction of his desk was much sturdier than that of a mere finger, and that he was unlikely to move it as it was right next to the fireplace and got a nice bit of light from the window.

The debate reached crisis point in 1712 when Carelli lost three fingers from his left hand in a tragic counting accident, and was unable to recover them in time for preservation. Upon hearing the news, Boger rushed to his writing desk to prepare a gloating letter, only to discover that the desk had been stolen the previous night; presumably, he conjectured, as part of an attempt to extract the centimetre and sell it on the black market. Keen to prevent their creation from falling into the wrong hands, Boger and Carelli agreed to meet halfway in order to settle the matter like gentleman. Several heated letters later, they concluded that ‘halfway’ was located somewhere between the bar and the billiards room of a small pub in Copenhagen, and they convened at the Hviids Vinstue inn on the 12th of December 1712, finally emerging two days later on the 14th with a written agreement and severe bruises on their faces and bodies.

A beermat from the Timkeeper er Sammenslutning af Danmark collection In a jointly published article for the journal of the Association Internationale d’Métriques (International Metric Association), they stated that a centimetre was henceforth to be defined as “the exact width of five Danish beermats”, with a millimetre being defined as “precisely half of one Danish beermat”, and a metre being defined as “an indeterminate amount of Danish beermats, roughly equivalent to the height of one Danish beer keg”.

The beermats in question are now held in trust by the Timkeeper er Sammenslutning af Danmark (Timekeeper’s Association of Denmark), who are responsible for maintaining the Danish Mean Centimetre, which they periodically adjust due to the increased accuracy of modern measuring techniques, and the slow but erratic degeneration of the beermats.

Thanks to the vision and dedication of Boger and Carelli, centimetres are now known to every schoolchild, and can be purchased in batches of 30 from most good stationery shops, or by sending a stamped addressed envelope of at least 1 cm in length and height to the following address:

Dancing Henry Metrological Supplies,
Block 27A, Sir Henry Drummond Estate,