Passage 10.19.9
ὁ δὲ ἀθροισθεὶς στρατὸς πεζοὶ μὲν μυριάδες ἐγένοντο πεντεκαίδεκα προσόντων σφίσι δισχιλίων, οἱ δὲ ἱππεύοντες τετρακόσιοι καὶ δισμύριοι. τοσοῦτοι μὲν ἦσαν τῶν ἱππέων τὸ ἀεὶ ἐνεργόν, ἀριθμὸς δὲ αὐτῶν ὁ ἀληθὴς διακόσιοί τε καὶ χίλιοι καὶ ἓξ μυριάδες· δύο γὰρ οἰκέται περὶ ἕκαστον τῶν ἱππευόντων ἦσαν, ἀγαθοὶ καὶ αὐτοὶ τὰ ἱππικὰ καὶ ἵππους ὁμοίως ἔχοντες.
The army, when assembled, consisted of fifteen myriads of infantry, with an additional two thousand men, and twenty thousand four hundred cavalry. Such was the number of horsemen always actively engaged; but their true total amounted to sixty-one thousand two hundred. For each cavalryman had two attendants, themselves skilled horsemen and likewise provided with horses.