  I use archival data to measure the mass of the central black hole in NGC
4526, M = (4.70 +- 0.14) X 10^8 Msun. This 3% error bar is the most precise for
an extra-galactic black hole and is close to the precision obtained for Sgr A*
in the Milky Way. The factor 7 improvement over the previous measurement is
entirely due to correction of a mathematical error, an error that I suggest may
be common among astronomers.
