Garudapurana 1.43.13

1.43.13

sauvarṇe rājate tāmre vaiṇave mṛnmaye nyaset /
aṅguṣṭhena catuḥ ṣaṣṭiḥ śreṣṭhaṃ madhyaṃ tadardhataḥ //

One should place it in a vessel of gold, silver, copper, bamboo, or clay. / Sixty-four [threads] measured by the thumb is best, half of that is middling,