There are four asanas you may perform mentally. This is the entirety of Jnana Yoga.
Develop awareness of the body. Watch as you hold an arm still. Watch yourself in any asana. Breathe, counting heartbeats - to better hear your heart: 1 heartbeat, 2 heartbeats, breathe in and hold for 10 heart beats. Sense every fluid in your body, all the air, every muscle, every tendon, the hair touching your clothes, every bone. Smell your nose, taste your mouth, see your eye, hear your ears, feel your skin. Use your body to sense your body. Protect your body from unnecessary harm, either arising from action or inaction. Body is the first jnana.
The sensation is observed through mind: what is smelled, tasted, seen, heard, felt is understood through past experience and the anticipation of future experience, in the context of self and not-self, and other such association. Such bias teaches against trusting sensation, or observation. Bias is the foundation of belief. There is also much which is not sensed, or which is ignored. Ignorance is the foundation of desire. Use your mind to observe your mind if you would protect your mind against desire and belief. Mind is the second jnana.
This observation is evaluated through consciousness, through complex emotional processes. The act of remembrance, the act of anticipation, all those numerous acts of observation and association produces thought, chemical reactions in the brain which are understood as emotion. Thought, as the basis of all such consideration, may also be considered and evaluated: good and bad, liked and disliked, pleasant and painful. Consideration results in instinctive responses. Some sensations are sought, others avoided. Think about thought: emotion, arising as the effect of mind, arising out of the stimulation, is not itself proximate to reality and is inappropriate to act upon. Act upon reality, not your perception of it. Thought is the third jnana.
Thought is understood in the context of self, identity, what theists call “soul.” I like this, I dislike this, this is Mine, this is not Mine, this is what I am, this is not what I am. I, me, mine. From identity, self, ego, soul - from this attachment results in aggression, acting upon the ignorance and desire of thought and mind, which arise out of body. But understanding can itself be understood. Understanding is the fourth jnana.
Understanding understanding means understanding your nature, your dharma. The implication of self-awareness is that self can be controlled by self. This is the foundation of wisdom, of enlightenment, of Bodhi. For it is by effort in self-control that the skill is perfected into numerous siddhis. And by siddhi that contentment (riddhi) is obtained through self-sacrifice.
Jnana (jhana) is a state of rest. It is an asana. It is the means by which increasing awareness is achieved. As you would wake yourself from sleep, rouse yourself from this rest. “Rest” merely implies an inertial resistance: when you are asleep, you tend to stay asleep; when you are awake, you tend to stay awake. Withdraw from sleep, and you wake.
In the first jhana, withdraw from sensuality (touch, taste, sound, sight, smell, etc.): this heightens your ability to think in evaluation.
In the second jhana, withdrawal from thinking in evaluation: this heightens your ability to understand awareness and consciousness.
In the third jhana, where there is awareness of pleasure and pain, freedom of thought and evaluation, freedom of sensuality, you are able to withdraw from elation and distress.
In the fourth jhana you may then withdrawal from seeking pleasure and avoiding pain, or any instinctual response: you may become self-controlled and rational.
In the fourth jhana, direct your mind to withdraw from time, space, form: an increased consciousness and logicality naturally arises. This increased consciousness is necessary for true love: love arises by a knowledge of the nature of things. By merely understanding the basic laws of the universe, freedom from the cycles of suffering is possible. At this stage, there is only wakefulness to truth, and then enlightenment.
It is your nature to self-improve, to become more than you are, to change your nature for something better. This is your Dharma.