Vijñāna Bhairava Tantra 1.64

1.64

मध्यजिह्वे स्फारितास्ये मध्ये निक्षिप्य चेतनाम् । होच्चारं मनसा कुर्वंस्ततः शान्ते प्रलीयते ॥६४॥

madhyajihve sphāritāsye madhye nikṣipya cetanām | hoccāraṃ manasā kurvaṃs tataḥ śānte pralīyate

anuṣṭubh

— in the middle of the tongue ; — with mouth opened wide ; — having cast into the middle ; — the awareness ; — the utterance of HA ; — performing with the mind ; — thereupon, in the Peaceful (state) ; — (the yogin) dissolves

With tongue placed in the middle (of the open palate), with mouth open, placing consciousness in the middle, mentally uttering 'ha' — one dissolves into the Peaceful.