"In Einstein’s corrected formula m has the value m=\frac {{m}_}{\sqrt} where the “rest mass” m0 represents the mass of a body that is not moving and c is the speed of light, which is about 3×105 km⋅sec−1 or about 186,000 mi⋅sec−1."
January 1, 1970
https://en.wikiquote.org/wiki/Speed