[jzemeocala]

well the Pythagorean comma and how to divide it amongst the octave was the central objective during the whole evolution of temperament (from meantone to modern day 12-tet). So that takes us back to at least the 15th/16th century

[dr_dshiv]

Aristoxenus (Pythagorean student of Aristotle) seemed to have developed a proto-equal temperament system.

Written about by this guy (not peer reviewed, but has good presentation of the original Aristoxenus) https://siementerpstra.com/aristoxenus/

http://terpstrakeyboard.com/about/

[ofalkaed]

That is more theory than practice unless you want to reduce Pythagoras down to a comma. I was referring more to people who decided to take Pythagoras and related writings as gospel.