Vaishnava Dharmashastra 19.7

19.7

pretasyodakanirvapaṇaṃ kṛtvaikaṃ piṇḍaṃ kuśeṣu dadyuḥ ||

After having offered a libation of water to the deceased, they must place one ball of rice on blades of Kusa grass, (and this ceremony has to be repeated on each subsequent day, while the period of impurity lasts.)