16. asanasthah sukham hrade nimajjati //
Seated in that real posture, he effortlessly dives in the ocean of nectar.
“Actually, the postures (asanas) explained in the yogadarsana are not really asanas at all. Sivayoga is the only posture that must be understood when you are seeking to understand the real posture for such a yogi. This real posture is the supreme energy of awareness. You are seated in that posture when you hold and possess the supreme energy of awareness. Then in each and every act of your life you are aware, you are seated in that posture. This is the real asana. The physical postures called asanas are not actually asanas. These so-called asanas are only imitations of the real asana. They are only imagination. The real asana actually exists when you are truly residing in the state of absolute awareness, the awareness of self.
The yogi who, leaving aside the effort of asana (yogic exercises), pranayama (breathing exercises), dhyana (contemplation), and dharana (meditation), simply remains in that posture with nothing left to do, aware of what he actually is. This is why the author has used the word sukham in the sutra because "effortlessly" means that without exerting any effort in respect to breathing or yogic exercise, contemplation or meditation, he remains seated in that posture.
So in an internal, not external, way he perceives the reality of his embodiment of awareness (You must not be aware of your dress, your beauty, or charm, or your body—You must be aware of your nature, what you really are—That is, in the real sense, awareness) and without any effort finally immerses himself in the ocean from which the universe rises and expands. He dives and enters for good in that ocean, which is filled with real nectar.
What does diving mean? In diving into the ocean of nectar, he lets the impressions of the body (deha), of the breath (prana), of the eight constituents (puryastaka) and of the void (sunya) sink into that ocean and he becomes one with that nectar. This is the real way of diving.
In Mrityujita Tantra (Netra Tantra), it is said:
You do not have to concentrate above on sahasrardha cakra or below on muladhara cakra. You have not to concentrate on the tip of the nose, on the backside, or on the nostrils – breathing and exercising prana and apana.
Nor do you have to concentrate on someplace in your body or concentrate in a universal way. You do not have to put your concentration on ether nor do you have to concentrate downward.
You do not have to close your eyes. You do not have to open your eyes and keep your eyes wide open. You do not have to take any support in meditation, nor do you have to have absence of support.
You do not have to concentrate on your organic field, or on the universal elements, or on sensations of the five senses – sound (sabda), touch (sparsa), sight (rupa), taste (rasa) and smell (gandha). You have to put all of these aside and enter into that universal being of awareness. This is what Saivaite yogis do successfully.
Actually, this state of the Saivaite yogi is the real state of Siva. This state is not revealed to others; it is revealed only to the revealers.

~ Mrityujita Tantra 8.41-45

This state, which is the real nature of Siva, is not revealed; this state is the revealer. This state is subjective, not objective. So the aspirant must be active in an interior way, not in an external way. He must be active in being aware of himself. That is real activity. Real activity is not moving about here and there. The revealed is not the point to be sought; it is the revealer that is to be striven for. And this state of the revealer is not separate from subjective consciousness. It is only subjective consciousness.”

~ Siva Sutras: The Supreme Awakening as Revealed By Swami Lakshmanjoo