The Law Code of Nārada m1.15

m1.15

rājā sapuruṣaḥ sabhyāḥ śāstraṃ gaṇakalekhakau /
hiraṇyam agnir udakam aṣṭāṅgaḥ sa udāhṛtaḥ //

Because it consists of these eight, the king, his dutiful officer, the assessors of the court, the law-book, the accountant and scribe, gold, fire, and water; therefore it is said to have eight members.