CC Madhya 15.204
eka-ghare śālagrāmera bhoga-sevā haya
Among the followers of the Vedic way, the śālagrāma-śilā, the vigraha of Nārāyaṇa, is worshiped in the form of a stone ball. In India, every brāhmaṇa still worships the śālagrāma-śilā in his home. The vaiśyas and kṣatriyas may also engage in this worship, but it is compulsory in the house of a brāhmaṇa.