That reminds me of Tiffany's marriage agreement with Rob Anybody

At the end of the world is a great big mountain of granite rock a mile high,' she said. 'And every year, a tiny bird flies all the way to the rock and wipes its beak on it. Well, when the little bird has worn the mountain down to the size of a grain of sand . . . that's the day I'll marry you, Rob Anybody Feegle!