Relieving hunger with a picture of cakes
Once in the Three Kingdoms Period (220-280)， the duke of the Wei, Cao Rui, planed to select a very capable man to work for him. He said to his ministers: 'When choosing a talented person, always beware of one with a false reputation. A false reputation is just like a picture of a cake; it can' t ease hunger.'
Later, this idiom came to be used to mean comforting oneself with unrealistic thoughts, without solving practical problems。