In Chapter 2 of his novel Pantagruel François Rabelais writes (quoted from the edition on Wikisource)
Le philosophe racompte en mouvant la question, pourquoy cest que leau de la mer est sallee ? quau temps que Phebus bailla le gouvernement de son chariot lucificque à son fils Phaeton : Ledict Phaeton mal apris en lart, et ne scavant ensuyvre la ligne eclipticque entre les deux tropicques de la sphere du Soleil, varia de son chemin : et tant approcha de la terre, quil mist a sec toutes les contrees subiacentes, bruslant une grande partie du ciel, que les philosophes appellent via lactea : et les Lifrelofres nomment le chemin sainct Jacques. Adonc la terre fut tant eschauffee, quil luy vint une sueur enorme, dont elle sua toute la mer, que par ce est sallee (...)
In the translation by Thomas Urquhart and Peter Antony Motteux, this passage reads as follows:
The philosopher reports, in moving the question, Wherefore it is that the sea-water is salt, that at the time when Phoebus gave the government of his resplendent chariot to his son Phaeton, the said Phaeton, unskilful in the art, and not knowing how to keep the ecliptic line betwixt the two tropics of the latitude of the sun's course, strayed out of his way, and came so near the earth that he dried up all the countries that were under it, burning a great part of the heavens which the philosophers call Via lactea, and the huffsnuffs St. James's way; although the most coped, lofty, and high-crested poets affirm that to be the place where Juno's milk fell when she gave suck to Hercules. The earth at that time was so excessively heated that it fell into an enormous sweat, yea, such a one as made it sweat out the sea, which is therefore salt, because all sweat is salt (...)
Rabelais writes "the philosopher", as if it would be obvious who he has in mind. However, I could not find anything about the sea's salinity in the Wikipedia article about Phaeton, even though the text cites several versions of the story: Plato, Ovid, Clement of Alexandria, Suetonius, Euripides and Lucian. Among these, only Plato and Clement of Alexandria are known as philosophers. I checked Clement of Alexandria's Stromata, but this text mentions Phaeton only briefly (though several times). Assuming that Rabelais is not leading us up (or down) the garden path, who is the philosopher he is referring to?