Laudator Temporis Acti

Plutarch, To an Uneducated Ruler 7 = Moralia 782 E-F (tr. Harold North Fowler):

Nor is it possible in positions of power for vices to be concealed. Epileptics, if they go up to a high place and move about, grow dizzy and reel, which makes their disease evident, and just so Fortune by such things as riches, reputations, or offices exalts uneducated and uncultured men a little and then, as soon as they have risen high, gives them a conspicuous fall; or, to use a better simile, just as in a number of vessels you could not tell which is whole and which is defective, but when you pour liquid into them the leak appears, just so corrupt souls cannot contain power, but leak out in acts of desire, anger, imposture, and bad taste.

οὐδὲ γὰρ λαθεῖν οἷόν τε τὰς κακίας ἐν ταῖς ἐξουσίαις· ἀλλὰ τοὺς μὲν ἐπιληπτικούς, ἂν ἐν ὕψει τινὶ γένωνται καὶ περιενεχθῶσιν, ἴλιγγος ἴσχει καὶ σάλος, ἐξελέγχων τὸ πάθος αὐτῶν, τοὺς δ᾽ ἀπαιδεύτους καὶ ἀμαθεῖς ἡ τύχη μικρὸν ἐκκουφίσασα πλούτοις τισὶν ἢ δόξαις ἢ ἀρχαῖς μετεώρους γενομένους εὐθὺς, ἑπιδείκνυσι πίπτοντας· μᾶλλον δ᾽, ὥσπερ τῶν κενῶν ἀγγείων οὐκ ἂν διαγνοίης τὸ ἀκέραιον καὶ πεπονηκός, ἀλλ᾽ ὅταν ἐγχέῃς, φαίνεται τὸ ῥέον· οὕτως αἱ σαθραὶ ψυχαὶ τὰς ἐξουσίας μὴ στέγουσαι ῥέουσιν ἔξω ταῖς ἐπιθυμίαις, ταῖς ὀργαῖς, ταῖς ἀλαζονείαις, ταῖς ἀπειροκαλίαις.