Kautilya's Arthashastra 3.6.17

3.6.17

cāturvarṇyaputrāṇāṃ brāhmaṇīputraś caturo 'ṃśān haret, kṣatriyāputrastrīn aṃśān, vaiśyāputro dvāv aṃśau, ekaṃ śūdrāputraḥ //

Of sons begotten by a Bráhman in the four castes, the son of a Bráhman woman shall take four shares; the son of a Kshatriya woman three shares; the son of a Vaisya woman two shares, and the son of a Súdra woman one share.