True, but it was the 18th century. They could measure earthly things well enough, not so much photons.

It’s a bit of a shame it wasn’t redefined as 1/300,000,000th of the distance light travels in a second when it was redefined, but the redefinition was about 50 years too late for that to happen. A difference of 0.07% in the base unit of measurement used by all science would’ve been far too much for 2019, given all the precision measurements we do these days.