Full Idea
When our predecessors discovered musical scales, they also discovered similar features in bodily movement, which should also be measured numerically, and called 'tempos' and 'measures'.
Gist of Idea
When musical harmony and rhythm were discovered, similar features were seen in bodily movement
Source
report of Pythagoras (reports [c.530 BCE]) by Plato - Philebus 17d
Book Reference
Plato: 'Philebus', ed/tr. Waterfield,Robin [Penguin 1982], p.62