According to legend, why does Narcissus stare in the lake?
The Greek legend or myth of Narcissus involves a notion of unhealthy love of self. The beautiful son of the river god was the object of everyone's desire. His beauty inspired declarations of love from many. He rejected them all. One day, he gazes upon his own reflection in a lake. He is immediately taken back with the beauty of that which stares back at him. Narcissus stares in the lake because he is in love with his own reflection. He is so much in love with the reflection that stares back at him that he leans over the edge of the bank to get a closer and more intimate view. In doing so, he falls into the water and then dies. Narcissus' love of self- beauty is what causes him stare into the lake, leading to his death.
Coelho takes a slant on this myth with referencing Wilde's interpretation of the myth. In Wilde's vision, the lake did not recognize Narcissus, even though everyone else did. The lake weeps not because of Narcissus' self love, but that within Narcissus eyes and his incessant staring, the lake realized her own beauty in how someone looked at her with such longing. There is beauty reflected in all of the world becomes the message out of this application of the myth.