Pitṛgaṇa-Vibhāga (Classification of the Pitṛs) and the Śrāddha–Soma Nourishment Cycle
त्रसरेणुप्रमाणानि तेषु चावस्थितान्पितॄन् / सुसूक्ष्मानपरिव्यक्तानग्नीनग्निष्विवाहितान्
trasareṇupramāṇāni teṣu cāvasthitānpitṝn / susūkṣmānaparivyaktānagnīnagniṣvivāhitān
Within them dwelt the Pitṛs, no larger than a trasareṇu—exceedingly subtle and unmanifest, like fire borne hidden within fire.