Āpta Pramāṇa - आप पम्ग Kumbhaka Paddhathih, Verse 28

सुषुम्पग्ून ूत्न निनव्ककेि चेूस् व्रचेिष-म्गून चरनग सरऽप्-कुम् कृवरनदू् suṣumṇāntargataṃ tasyāṃ nirvikalpena cetasā dhārayen-mārutaṃ yogi so'ntaḥ-kumbhaḥ śivoditaḥ

Akashic Revelation When the marut (prana) is retained in sushumna without any mental distraction by a yogi, it is called antah-kumbhaka by Siva.