Reduction of the effective mass of the Reissner-Nordstrom spacetime

We derive the Teixeira, Wolk and Som method, for obtaining electrostatic solutions from given vacuum solutions, in its inverse form. Then we use it to obtain the geometrical mass $M_S$ in the Schwarzschild spacetime, and we find $M_S^2=M^2-Q^2$, where $M$ and $Q$ are, respectively, the mass and charge parameters of the Reissner-Nordstr"om spacetime. We compare $M_S$ to the corresponding active gravitational mass and mass function.