I'm looking for a LGB for a friend:
A boy receives a picture from his grandpa or uncle. He is told the picture contains an image of his birthday/Christmas present. The boy stares at the picture for a long time in every way possible, but cannot see anything in the picture.

Just at the boy figures out what it is - the relative shows up at the door with his present - a boat.

She describes it as an optical illusion picture that the boy is trying to look at.

Any ideas?

Thanks!