Passage 9.31.1
καὶ Ἀρσινόης ἐστὶν ἐν Ἑλικῶνι εἰκών, ἣν Πτολεμαῖος ἔγημεν ἀδελφὸς ὤν. τὴν δὲ Ἀρσινόην στρουθὸς φέρει χαλκῆ τῶν ἀπτήνων· πτερὰ μέν γε καὶ αὗται κατὰ ταὐτὰ ταῖς ἄλλαις φύουσιν, ὑπὸ δὲ βάρους καὶ διὰ μέγεθος οὐχ οἷά τέ ἐστιν ἀνέχειν σφᾶς ἐς τὸν ἀέρα τὰ πτερά.
On Helicon there is also a statue of Arsinoe, whom her brother Ptolemy married. Arsinoe is carried by an ostrich, a bronze figure of a winged bird; although these birds also produce feathers similar to other birds, owing to their weight and size, they are unable to lift themselves into the air by means of their feathers.