Hathayoga 1-45

नासनं सिद्ध-सदृशं न कुम्भः केवलोपमः ।
न खेचरी-समा मुद्रा न नाद-सदृशो लयः ॥ ४५॥

Nāsanam siddhasadrśam na kumbhah kevalopamah Na khecharīsamā mudrā na nādasadrśo layah

There is no Âsana like the Siddhâsana and no Kumbhaka like the Kevala. There is no mudrâ like the Khechari and no laya like the Nâda (Anâhata Nâda.)