Max Planck: He has a rightful place within the continuum of development of an accurate definition of the speed of light. The chart below is from Wikipedia with a single line that has been added. Take Planck’s Length — 1.616255×10-35 meters — divided by Planck’s Time — 5.391247×10-44 seconds and you have 299,792.4228 kilometers per second.
The chart above and the description that follows were both deleted by the Wikipedia editors responsible for this page.
“In 1899 Max Planck defined Planck Time as the unit of time (in a system of natural units or “Planck units”) whereby light travels the distance of one (1) Planck length in a vacuum. The calculation, Planck Length divided by Planck time is equal to 299,792,422.79 meters/second.”
van Remortel, N. The nature of natural units. Nature Phys 12, 1082 (2016). https://doi.org/10.1038/nphys3950