De institutione musica I.5: Quae inaequalitatis species consonantiis deputentur.
Of these kinds of inequality, then, the last two are to be set aside, since they are mixed from the former; but the first three call for investigation. The multiple seems to have the greater power toward consonances, the superparticular the next; the superpartient, however, is excluded from the concord of harmony, as it seems to some, though not to Ptolemy.