# Did anybody consider the product of the principal curvatures before Gauss?

Gauss proved that the so-called Gaussian curvature is an intrinsic invariant of the surface, even though it is defined extrinsically as the product of the principal curvatures of a Euclidean embedding. But apart from the issue of its intrinsic nature, did anyone consider the invariant given by the product of the principal curvatures before Gauss?