François-Ambroise Didot Revises Fournier's Point System for Typographic Units

In 1775 French printer François-Ambroise Didot revised the point system for typographic units introduced by Pierre-Simon Fournier in 1737.

Didot related the body size of the type to the legal standard of measurement then in force in France, the "pied du roi" or "royal foot." This resulted in an augmentation of Fournier's point by a twelfth. 

In Didot's point system:

• 1 point = ¹⁄₆ ligne = ¹⁄₇₂ French Royal inch = ^{15 625}⁄_{41 559} mm ≤  0.375 971 510 4 mm, however in practice mostly: 0.376 000 mm, i.e. + 0.0076%

Didot's point system became the standard unit of type measurement in France. It was adopted in Germany in the mid-19th century.