Garudapurana 2.35.34

2.35.34

śmaśānavāsibhūtebhyaḥ pañcamaṃ prativeśyakam /
ṣaṣṭhaṃ sañcayane proktaṃ daśa piṇḍā daśāhikāḥ /
śrāddhaṣoḍaṣakañcaitat prathamaṃ parikīrtitam //

the fifth for the spirits dwelling in the cremation ground, the neighborly one, / the sixth is taught at the collection of bones, and ten rice-balls for the ten days; / this is proclaimed as the first set of sixteen śrāddhas.