First widely known absolute pitch determination?

A historical question. At what period in music/acoustic history did
the measurement of pitch by Hertz or cps become commonly known and
useful? When did tuning forks (etc.) start to have their pitch in Hz
stamped on them? What methods were used to measure and check pitch?

What I have found suggests that Sauveur was an important figure in the
early scientific development, but details are lacking.

~~~Thomas~~~