There is no āsana like Siddhāsana, no kumbhaka like Kevala, no mudrā like Khecarī, no laya like Nāda.

This verse presents the four supreme practices of Haṭha Yoga in a memorable synthesis:

1. Siddhāsana — The best āsana. Not because of its difficulty, but because of its efficacy in stabilizing prāṇa and mind.

2. Kevala Kumbhaka — The spontaneous retention of breath, without effort. It occurs naturally when prāṇa enters suṣumnā. It is the goal of all prāṇāyāma.

3. Khecarī Mudrā — The “seal that moves in space.” It involves rolling the tongue backward to seal the soft palate. It awakens the flow of amṛta (nectar) from the brain.

4. Nāda — The internal sound (anāhata nāda). Listening to it leads to laya (absorption). It is the central topic of the fourth chapter.

These four practices represent the essence of the Haṭha system: one posture, one breath, one seal, one sound. Everything else is preparation or variation.