What does a hungry ghost look like? It has a stomach of the size of Mount Meru and a throat as thin as a needle. Think about this: When greed arises, a person’s generosity then becomes as thin as a needle whereas his greed grows to the size of Mount Meru. When he sees other’s riches, his envy burns like fire, just like the flames that the hungry ghost spew out of their mouths. Nothing can satisfy our greed, just as the hungry ghosts can’t swallow anything, nor digest any food, and the food would turn into poison. We therefore must practice by using our greed to vicariously feel the sufferings of the hungry ghosts.

-- 17th Karmapa, Ogyen Trinley Dorje