Pluto is so distant that it is difficult to learn much about it from direct observation. For example, starting more than 100 years ago, astronomers first postulated its existence and began estimating its mass by assuming it was responsible for observed perturbations of the orbits of Neptune and Uranus. Succeeding estimates of mass were made by the most eminent astronomers of the time; for example, estimates were made by astronomers such as Pickering, Lowell, Nicholson, Mayall, Eckert, Brouwer, and Clemence, with the latest estimate being made in 1978 by Christy and Harrington. At the recent meeting of the 50th Anniversary of the Discovery of Pluto, R. L. Duncombe and P. K. Seidelman assembled these earlier estimates of the mass of Pluto. We have plotted these (see figure), starting with the estimate by J. Babinet in 1848 which gave Pluto a mass 12 times that of Earth. The graph clearly illustrates that while Pluto was sighted in 1930, it was slighted in the 1970's.