Aelian, Historia Varia 9.13:
They say that Philetas of Cos was extremely thin. And so, because he could be easily knocked over on any account, they say that he had soles fashioned from lead in his shoes, so that he wouldn’t be knocked over by the winds if they happened to be blowing hard. But if he was thus unable to bear up against the force of the wind, how was he able to lift the burden of his shoes? I am not at all persuaded by this story, but I have simply said what I have learned about this man.
Φιλητᾶν λέγουσι τὸν Κῷον λεπτότατον γενέσθαι τὸ σῶμα. ἐπεὶ τοίνυν ἀνατραπῆναι ῥᾴδιος ἦν ἐκ πάσης προφάσεως, μολίβδου φασὶ πεποιημένα εἶχεν ἐν τοῖς ὑποδήμασι πέλματα, ἵνα μὴ ἀνατρέπηται ὑπὸ τῶν ἀνέμων, εἴ ποτε σκληροὶ κατέπνεον. εἰ δὲ ἦν οὕτως ἀδύνατος, ὥστε μὴ ἀντέχειν πνεύματι, πῶς οἷός τε ἦν τοσοῦτον φορτίον ἐπάγεσθαι; ἐμὲ μὲν οὖν τὸ λεχθὲν οὐ πείθει· ὃ δὲ ἔγνων ὑπὲρ τοῦ ἀνδρός, τοῦτο εἶπον.
Athenaeus, Deipnosophistae 12.552
Philetas, the poet from Cos, was rather thin, and had around his feet balls made of lead to compensate for the lightness of his body and prevent him from being blown over by the wind.
λεπτότερος δ’ ἦν Φιλήτας ὁ Κῷος ποιητής, ὃς διὰ τὴν τοῦ σώματος ἰσχνότητα σφαίρας ἐκ μολίβου πεποιημένας εἶχε περὶ τὼ πόδε, ὡς μὴ ὑπὸ ἀνέμου ἀνατραπείη.