These well temperaments share certain characteristics. They all minimize the size of the 
major thirds in the vicinity of C on the circle of fifths, and keep the most extreme M3s to 
exactly or just under the "maximum" of 21.51 cents. These widest thirds are called 
Pythagorean Thirds because they are formed by the Pythagorean rule of tuning a series of 
four perfect fifths. (For example, the sequence C-F-Bb-Eb-Ab is tuned with perfect fifths, 
resulting in a major third Ab-C that measures 21.51 cents wide of just. 
This principle can be observed exactly in Werckmeister, Kirnberger, and Prinz, and 
a fifth lower in Vallotti and Young.)