From The Aesop's Fables : The Farmer & His Sons

A farmer was about to die and decided to tell them a secret, he called them round him and said, 'My sons I am about to die I want to tell you that in my vineyard there lies a hidden treasure. Go dig and you will find it.' As soon as their father was dead, the sons took spade and fork and digged up the soil of the vineyard over and over again, the treasure was supposed to be buried there but they found nothing. The vines after those digging produced a crop such as had never seen before.