De institutione musica IV.12: Ratio superius dispositae descriptionis.
In the figure above, then, proslambanomenos holds the consonance of the octave with mese, mese with nete hyperboleon, and proslambanomenos the double octave with nete hyperboleon; the consonance of the fourth is kept by hypate hypaton with hypate meson, hypate meson with mese, mese with nete synemmenon, paramese with nete diezeugmenon, nete diezeugmenon with nete hyperboleon, and this so that in these consonances we count whole tetrachords. And that the whole order of the strings in this figure according to the three kinds may be seen more clearly, only five tetrachords are noted: the first and deepest the hypaton, whose first is hypate hypaton and last hypate meson; the second the meson, whose first is hypate meson and extreme mese; the third the synemmenon, whose first is mese and final nete synemmenon; the fourth the diezeugmenon, whose first is paramesos and extreme nete diezeugmenon; the fifth the hyperboleon, whose first is nete diezeugmenon, and it is terminated at the extreme nete hyperboleon.