Manavashrautasutra 11.2.7

11.2.7

tatrābhiṣekaṃ kurvīta pituḥ śiśor jananyā devarasyākṛtyāsandyām āsīnānām̐ saṃpātenābhiṣiñcati śiraso 'dhy ā mukhāt //

There he should perform the sprinkling: for the father, the infant, the mother, and the brother-in-law, who are seated on a wicker seat, he sprinkles with the residue [of the water] from the head down over the face.