Pausanias Description of Greece 1.22.5

[5] For the ship that carried the young people to Crete began her voyage with black sails; but Theseus, who was sailing on an adventure against the bull of Minos, as it is called, had told his father beforehand that he would use white sails if he should sail back victorious over the bull. But the loss of Ariadne made him forget the signal. Then Aegeus, when from this eminence he saw the vessel borne by black sails, thinking that his son was dead, threw himself down to destruction. There is at Athens a sanctuary dedicated to him, and called the hero-shrine of Aegeus.

[5] I say-this-because [ gar] the ship that carried the young people to Crete began its voyage with black sails; but Theseus, who was sailing off on his daring-adventure [ tolmē] against the bull of Minos, so it is called, had told his father beforehand that he would use white sails if he should sail back victorious over the bull. But he had a memory-loss [ lēthē] of these things after Ariadne was taken from him. So, Aigeus, when from this vantage-point he saw the vessel carried along [ komizesthai] by black sails, thinking that his son was dead, threw himself down to destruction. There is in Athens a hero-shrine [ hērōion] that is named as belonging to Aigeus.