I found by experiment that it is neither, but an approximation to the tractrix (a modification of the catenary), if anything definite; as indeed one, on thinking over the matter, might feel certain it would be -- the tractrix being the curve of least friction.    From Wordnik.com.  [Men of Invention and Industry] Reference

This had led, through the work of Leonardo (on the catenary-tractrix matter), into the work of Kepler, which, in turn, led into Leibniz's uniquely original discovery of the principle of the calculus, and the revision of that discovery by Leibniz, based upon the work of Pierre de Fermat, which was carried out by Leibniz's collaboration with Jean Bernouilli in defining a universal physical principle of least action.    From Wordnik.com.  [LaRouche's Latest] Reference

De Docta Ignorantia; Leonardo da Vinci (e.g., the use of the relatively least-action physical curve, the catenary-tractrix, as a principle of construction.    From Wordnik.com.  [LaRouche's Latest] Reference

The curve is a tractrix hybrid.    From Wordnik.com.  [All Discussion Groups: Message List - root] Reference

Leibniz's definition of dynamics, as a revived expression of the principle of dynamis expressed by Classical Sphaerics, as in the duplication of the cube by Archytas, and the consequences of this for Archytas 'associate Plato, defined the universal physical principle specific to both Leibniz's original definition of the calculus, in 1675, the addition of dynamics, during the 1690s, and his enhanced reworking of this as a universal, catenary-tractrix-cued, physical principle of least action, as cast in collaboration with Jean Bernouilli.    From Wordnik.com.  [LaRouche's Latest] Reference