διὰ λαμπροτάτου βαίνοντες ἁβρῶς αἰθέρος → passing lightly through clear-shining air (Euripides, Medea 829)
without external agency: P. ἀπὸ τοῦ αὐτομάτου.
voluntarily: P. and V. ἑκουσίως, or use adj.
