The Pleiades is a well-studied cluster with both white dwarfs and massive, young stars. We present new measurements of the radial velocities for both stars in the interferometric binary Atlas in the Pleiades star cluster using the spectral disentangling method. Our large collection of archival spectral data allows for more complete coverage of the radial velocity curve. We use these measurements along with interferometric measurements of sky position and visibilities, and lunar occultation measurements of positions on the sky orbit to more precisely measure the orbital parameters. We obtain a period of about 291 days and a separation of about 12 milliarcseconds. This in turn gives a more precise measurement of the stellar masses. Along with the evolutionary state of the Atlas stars from photometry and the cooling time of the white dwarfs, this greatly improves the initial mass determination of the Pleiades white dwarfs for the initial-final mass relation. We derive a mass for the primary star of 4.43 ± 0.15M and a mass for the secondary star of 2.28 ± 0.14M. We use spectral energy distributions (SEDs) with photometric observations and recorded spectra of Atlas to infer temperatures of the component stars. We create a color-magnitude diagram for the Pleiades and place the component stars on it through brightness ratios in the V and B bands derived interferometrically. We determine the age of the cluster through a non-traditional approach to isochrone fitting. We interpolate the isochrone to enable the prediction of magnitudes and colors through the mass of a given star. We determine the mass of the Pleiades massive white dwarf LB 1497 progenitor by taking the age from the isochrone fitting and the cooling time of LB 1497. As a massive white dwarf, it must be near to the mass limit at which stars become neutron stars instead. So by using the mass of the primary and the eclipsing binary to derive the mass of the white dwarf progenitor accurately, we are constraining the IFMR with a strong lower limit.