Plato, Letters 358e

Σωκράτης μέν ἐστιν περὶ ἀσθένειαν τὴν τῆς στραγγουρίας, ἐμὲ δὲ ἀφικόμενον ἐνταῦθα ἄσχημον ἂν εἴη μὴ διαπράξασθαι ἐφʼ ἅπερ σὺ παρακαλεῖς. ἐγὼ δὲ ταῦτα γενέσθαι ἂν οὐ πολλὴν ἐλπίδα ἔχω—διʼ ἃ δέ, μακρᾶς ἑτέρας δέοιτʼ ἂν ἐπιστολῆς ἥτις πάντα διεξίοι—καὶ ἅμα οὐδὲ τῷ σώματι διὰ τὴν ἡλικίαν ἱκανῶς ἔχω πλανᾶσθαι καὶ κινδυνεύειν κατά τε γῆν καὶ κατὰ θάλατταν οἷα ἀπαντᾷ, καὶ νῦν πάντα κινδύνων ἐν ταῖς πορείαις ἐστὶ μεστά. συμβουλεῦσαι μέντοι

is laid up with an attack of strangury; while if I were to go there, it would be humiliating if I failed to succeed in the task for which you are inviting me. But I myself have no great hopes of success (as to my reasons for this, another long letter would be required to explain them in full), and moreover, because of my age, I am not physically fit to go wandering about and to run such risks as one encounters both by sea and land; and at present there is nothing but danger for travellers everywhere.