Ἄπειρον γὰρ ἦγες ἱππέων πλῆθος, καθάπερ ἀνδριάντας ἐπὶ τῶν ἵππων ὀχουμένους, οἷς συνήρμοστο τὰ μέλη κατὰ μίμησιν τῆς ἀνθρωπίνης φύσεως· ἀπὸ μὲν τῶν ἄκρων καρπῶν ἐς τοὺς ἀγκῶνας, ἐκεῖθεν δὲ ἐπὶ τοὺς ὤμους, καὶ ὁ θώραξ ἐκ τμημάτων κατὰ τὸ στέρνον καὶ τὰ νῶτα συναρμοζόμενος, τὸ κράνος αὐτῷ προσώπῳ σιδηροῦν ἐπικείμενον ἀνδριάντος λαμπροῦ καὶ στίλβοντος παρέχει τὴν ὄψιν, ἐπεὶ μηδὲ κνῆμαι καὶ μηροὶ μηδὲ ἄκροι πόδες τῆς σκευῆς ταύτης ἔρημοι λείπονται. συναρμοζομένων δὲ αὐτῶν τοῖς θώραξι διά τινων ἐκ κρίκου λεπτοῦ πεποιημένων οἱονεὶ ὑφασμάτων οὐδὲν ἂν ὀφθείη τοῦ σώματος γυμνὸν μερος, ἅτε καὶ τῶν χειρῶν τοῖς ὑφάσμασι τούτοις σκεπομένων πρὸς τὸ καὶ καμπτομένοις ἐπακολουθεῖν τοῖς δακτύλοις.
(Julian, Or. 1 [Panegyric in Honour of Constantius] 37C-38A)
Your cavalry was almost unlimited in numbers and they all sat their horses like statues, while their limbs were fitted with armour that followed closely the outline of the human form. It covers the arms from wrist to elbow and thence to the shoulder, while a coat of mail protects the shoulders, back and breast. The head and face are covered by a metal mask which makes its wearer look like a glittering statue, for not even the thighs and legs and the very ends of the feet lack this armour. It is attached to the cuirass by fine chain-armour like a web, so that no part of the body is visible and uncovered, for this woven covering protects the hands as well, and is so flexible that the wearers can bend even their fingers. (tr. Wilmer Cave Wright)
Hat tip to Jeroen Wijnendaele!