  In the 17th and 18th centuries, several natural philosophers studied the
phenomenon of refraction and attempted to obtain the Snell law from various
assumptions. Lacking experimental data, it was generally believed that light
travels faster in a refracting medium than in air. In the present article, I
review the contributions to the problem of light refraction by Descartes,
Fermat, Huygens, Leibniz, Newton, Clairaut, and finally Maupertuis who
established a principle of least action based on his own approach to the
problem.
