George Macdonald said this quote

...[T]wo of you can be no match for the three giants, I will find you, if I can, a third brother, who will take on himself the third share of the fight, and the preparation...I will show him to you in a glass, and, when he comes, you will know him at once. If he will share your endeavors, you must teach him all you know, and he will repay you well, in present song, and in future deeds.'She opened the door of a curious old cabinet that stood in the room. On the inside of this door was an oval convex mirror...we at length saw reflected the place where we stood, and the old dame seated in her chair...at the feet of the dame lay a young man...weeping.'Surely this youth will not serve our ends,' said I, 'for he weeps.'The old woman smiled. 'Past tears are present strength,'said she.