The Gaze

And so Perseus sought out Medusa's lair, surrounded as it was by the petrified remains of previous visitors, and he found the Gorgon sleeping; Yes, even though he had the good old magic arsenal, Perseus was not so foolhardy as to wake Medusa. And even though her gaze could hardly be expected to turn anyone to stone while her eyes were closed, he used the device provided by Athena to avoid looking at Medusa directly. (This suggests that you could be turned to stone just by gazing at Medusa, though most versions of the myth have it that it was the power of her gaze that counted.)