The Law Code of Yājñavalkya 3.1.6

3.1.6

ūnadvivārṣikaṃ pretaṃ nidadhyur bāndhavā bahiḥ |
alaṃkṛtya śucau bhūmāv asthisaṃcayanād ṛte ||
nāsya kāryo 'gnisaṃskāro nāpi kāryodakakriyā |
araṇye kāṣṭhavat tyaktvā kṣipeyus tryaham eva tu ||
iti | (MDh 5.68–69)

"Kinsmen should deposit outside a deceased child under two years of age, / having adorned him, in pure ground, without collecting bones.
Neither cremation rites should be performed for him, nor the water rite. / Having abandoned him in the wilderness like a piece of wood, they should remain [impure] for only three days." / Thus. (MDh 5.68–69)