M0748 (not in Perry). Source: Daumas 280. This fable is not in Perry’s catalog, but it appears to be inspired by the debate between the Danube and the waters in the Speculum Sapientiae, 3.23.
747. Mare et Fluvii. In unum convenerant fluvii, mare ut accusarent quod se, simul atque eius intrassent aquas, dulces quamvis essent et potui apti, falsos et ad bibendum redderet inutiles. Quae mare cum audiisset, aegre ferens innoxium se culpari, “Nolite,” inquit, “aquas intrare postea meas, ne corrumpamini sale.”
All the fables are here, and with each fable you can see the notes at the bottom of the fable (in the book, the notes are in the back). For more information about the free PDF of the book, see this post. :-)