Philo Judaeus Legatio Ad Gaium 80

[80] And he looked upon himself as being in this respect superior to all of these beings, because each of them while he had his own peculiar honours had no claim to those which belonged to the others, but he in his envious ambition appropriated all the honours of the whole body of demigods at once, or I should rather say, appropriated the demigods themselves; transforming himself not into the triple-bodied Geryon, so as to attract all beholders by the multitude of his bodies; but, what was the most extraordinary thing of all, changing and transforming the essence of one body into every variety of form and figure, like the Egyptian Proteus, whom Homer has represented as being susceptible of every variety of transformation, into all the elements, and into the animals, and plants, which belong to the different elements. ¹