The Geometrical Foot in the Geodesy Classics

  Both Cassini and Mecain & Delambre talk about a geometrical foot that is one 6000th of a minute of arc. Cassini brings it up in De la Grandeur et de la Figure de la Terre. Mecain & Delambre mention it in the Preliminary Discussion of Base du Systeme Metrique, Vol. 1. The latter also cites an earlier article by Gabriel Mouton in Observationes diametrorum (1670).