Matsyapurana 69.38

69.38

āropya kalaśaṃ tatra dikpālānpūjayettataḥ
chidreṇa jalasampūrṇam atha kṛṣṇājinasthitaḥ
tasya dhārāṃ ca śirasā dhārayetsakalāṃ niśām //

He should place there a pitcher of water and worship the Guardians of the quarters (Dikpâla). There the devotee should sit on a black deer skin and over his head place the pitcher of water, after making a hole in its centre. He should allow the water to trickle, drop by drop on his head, and, in the same way, should allow a stream of milk to fall on the head of the symbol of Viṣṇu.—38-39.