Of all the yantras that are helpful to us in gaining wealth, kanak yantra is considered to be the best. The word kanak has literally speaking got two meanings. One is gold, the second wheat. The devotee of this yantra can never have want of wealth + reiches. Ravana (of Ramanyan Story) himself was a great devotee and worshipper of this yantra kanakdhara yantra. Thats the reason why he had made the entire Lanka of gold.