Kautilya's Arthashastra 14.3.14

14.3.14

yatra brāhmaṇam āhitāgniṃ dagdhaṃ dahyamānaṃ vā paśyet tatra trirātropoṣitaḥ puṣyeṇa svayaṃmṛtasya vāsasā prasevaṃ kṛtvā citābhasmanā pūrayitvā tam ābadhya naṣṭacchāyārūpaś carati //

Wherever one may happen to see the corpse burnt or just being burnt of a Bráhman who kept sacrificial fire (while alive), there one should fast for three nights; and having on the day of the star of Pushya formed a sack from the garment of the corpse of a man who has died from natural causes, and having filled the sack with the ashes of the Bráhman's corpse, one may put on the sack on one's back, and walk invisible to others.