Anandakanda 1.23.451

1.23.451

tatrāpyudakamālokya parīkṣeta surārcite /
gṛhītvā śuṣkavaṃśaṃ tu kṣipettoyasya madhyataḥ //

Observing the water there, one should test it, O you worshipped by gods:
having taken dry bamboo, one should throw it into the midst of the water;