Kuṇḍakapūva Jātaka (No.109)
The Bodhisatta was once a tree-sprite in a castor-oil tree and received worship and offerings from many people. Among them was a very poor man who, having nothing else to offer at the tree, took a cake made of husk powder. However, when he saw the other rich offerings, he felt that the sprite would never accept so humble a gift and wished to eat the cake himself. The tree-sprite appeared, took the offering, and revealed to the man that heaps of treasure lay buried under the tree. The man informed the king of this, and the king, in return, appointed him royal treasurer.
The story was told in reference to a poor man of Sāvatthi. Once the people of a whole street in that town pooled their resources in order to entertain the Buddha and his monks to a meal of rice-gruel and cakes. The poor man, unable to afford anything else, made a bran-cake and by sheer determination put it in the alms-bowl of the Buddha himself. When it became known that the Buddha had accepted it, people of all classes crowded round the man offering him wealth if he would share with them the merit he had gained. After consulting with the Buddha, the man accepted the offers, and the gifts he received amounted to ninety million. That same evening the king appointed him treasurer. J.i.422 f.