Διὰ τί πρὸς τὸν ἥλιον βλέψαντες πτάρνυνται μᾶλλον; ἢ διότι κινεῖ θερμαίνων; καθάπερ οὖν πτεροῖς θιγγάνοντες. ἀμφότεροι γὰρ τὸ αὐτὸ ποιοῦσιν· τῇ γὰρ κινήσει θερμαίνοντες ἐκ τοῦ ὑγροῦ θᾶττον πνεῦμα ποιοῦσιν. τούτου δὲ ἡ ἔξοδος πταρμός.
(Pseudo-Aristotle, Problēmata 961b)
Why is one more apt to sneeze after looking at the sun? Is it because the sun heats us and produces a disturbance? So it is the same thing as tickling with feathers. For both produce the same effect; for producing movement by heat they create breath faster from the moisture. The exit of this breath is a sneeze. (tr. Harris Rackham)