Become like a hollow bamboo

Relax the body completely.

Let the mind remain in its unformed state.

Become like a hollow bamboo

so that everything flows through.

Will Johnson 'The Song of Mahamudra'

Alignment is an ongoing process

Alignment is not a static condition that we seek to create and then maintain. It is an ongoing process that may change from moment to moment. Relaxation is not a static gesture. It too is an ongoing process. The body continues to let go of tension and yield to the appearance of  new areas of sensation that continually present themselves.

Will Johnston in "The Posture of Meditation" page 56

A balanced posture generates alert awareness

A balanced posture requires very little effort to sustain and allows the major muscles of the body to relax. This relatively small expenditure of energy, coupled with the phenomenon of relaxation, produces a distinct feeling tone of softness, ease, and vibratory flow. It also generates a natural condition of alert awareness. This dual condition of comfort in the body and relaxed alertness in the mind is the fruit of balance.

Will Johnson in "The posture of Meditation" page 20

Relaxation

Relaxation is a function of the body's ability to surrender its weight to the pull of gravity. If we are constantly bracing ourselves against the force of gravity, we cannot truly relax.

Will Johnson in "The Posture of Meditation" page39