When the general plan of the Metamorphoses had suggested itself to Ovid, there was no lack of material for him to use. All the best-known myths could be found in the works of Homer, or of the Greek dramatists, with which he would naturally be familiar from his schooldays. Moreover, the idea of collecting such tales into omnibus volumes was one that had already appealed to poets of the Hellenistic age. We know of such a compilation, the Ornithogonia, assigned to one Boios, which dealt with the transformation of men into birds, and Nicander of Colophon had been responsible for another collection, which Ovid probably used. In Rome itself, Ovid's friend and contemporary, Aemilius Macer, had translated the Ornithogonia, and the Greek Parthenius, tutor to Virgil and Tiberius, had produced a work entitled Metamorphoses. It is impossible to say how much Ovid may have derived from these earlier writings, but there is no doubt that, both in its scope, embracing some two hundred and fifty stories, and in the elegance of style and treatment, Ovid's Metamorphoses is unique. The narrative skill which the poet possessed was employed to weave his tales into one vast and elaborate tapestry – an appropriate metaphor, for the pictorial effect of Ovid's writing is sometimes overwhelming.