Matsyapurana 69.39

69.39

tathaiva viṣṇoḥ śirasi kṣīradhārāṃ prapātayet
aratnimātraṃ kuṇḍaṃ ca kuryāttatra trimekhalam //

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.