Claim: The Caccioppoli set, introduced by Sir Isaac Newton, defined the measure of the boundary of a set.
Evidence: The basic concept of a Caccioppoli set was firstly introduced by the Italian mathematician Renato Caccioppoli in the paper (): considering a plane set or a surface defined on an open set in the plane, he defined their measure or area as the total variation in the sense of Tonelli of their defining functions, i.e. of their parametric equations, provided this quantity was bounded.