The meter was also a bit of a gimmick, definitionally -- they wanted a unit that was about three (French/Paris) feet, but a definition that wasn't "my personal

The meter was also a bit of a gimmick, definitionally -- they wanted a unit that was about three (French/Paris) feet, but a definition that wasn't "my personal yardstick" so everyone would agree to it. So they played around with various definitions like the 2-second pendulum, until they found one which worked and produced a single indisputable length. (As opposed to picking something fundamental which was unrelated to previous units. Eg (not that they could have derived it at the time), the hydrogen line, the wavelength of the 1420MHz watering hole frequency, is human scale at about 21cm/8.3 inches, fundamental throughout the universe, and unrelated to previous units.)