Plato, Laws 816a

ἐλάττους αὖ, δειλὸς δὲ καὶ ἀγύμναστος γεγονὼς πρὸς τὸ σωφρονεῖν μείζους καὶ σφοδροτέρας παρέχεται μεταβολὰς τῆς κινήσεως· ὅλως δὲ φθεγγόμενος, εἴτʼ ἐν ᾠδαῖς εἴτʼ ἐν λόγοις, ἡσυχίαν οὐ πάνυ δυνατὸς τῷ σώματι παρέχεσθαι πᾶς. διὸ μίμησις τῶν λεγομένων σχήμασι γενομένη τὴν ὀρχηστικὴν ἐξηργάσατο τέχνην σύμπασαν. ὁ μὲν οὖν ἐμμελῶς ἡμῶν, ὁ δὲ πλημμελῶς ἐν τούτοις πᾶσι κινεῖται.

but when he is cowardly and untrained in temperance, he indulges in greater and more violent changes of motion; and in general, no one who is using his voice, whether in song or in speech, is able to keep his body wholly at rest. Hence, when the representation of things spoken by means of gestures arose, it produced the whole art of dancing. In all these instances, one man of us moves in tune with his theme, another out of tune.