Henry Léauté: the forgotten kinematician and discoverer of the cubic of stationary curvature equation

Henry Leaute (1847-1916) was a French kinematician who taught at the ecole polytechnique. In 1878, Leaute derived the cubic of stationary curvature (CSC) equation in its modern form which is widely applied as a tool for synthesizing path generator mechanisms. The deduction of CSC equation by Leaute is based on an earlier work from the French school due to A. Mannheim in 1872. According to historical bibliographical evidence, Leaute and Mannheim are recognized as the true discoverers of CSC equation. However, the subsequent literature on CSC equation does not acknowledge the aforementioned French contributions, by not giving them credit. In the present work, early investigations on CSC is reviewed by quoting excerpts from original works and the precedence of discovery to Leaute is clarified. Then, the mathematical treatment of Leaute is elaborated, followed by the discussion of a graphical procedure for tracing the CSC through an example. A brief review of other scientific works of Leaute is also included. At the end, it is recommended to consider terming the CSC equation alternatively as "Mannheim-Leaute equation".