Sundararājāsana

Nothing is fixed. All is in flux.
— physicist Alan Lightman

There is an international movement to honor Yogācārya B.K.S. Iyengar, in the way sages of the past have been honored, through naming a pose after him. Traditionally these poses were named after the sage's first name, such as the twisting Marīchyāsanas named for Sage Marīchi or Sage Vasistha, for Vasisthāsana (an arm balancing asana). The first two initials of his name stand for "Bellur" the small Indian village where he was born, and Krishnamachar, his father's name... S. is for Sundararāja. There are many ways to practice this asana, in Iyengar yoga classes, it is first introduced with the help of the chair.  There are efforts to rename this āsana, Dwi Pāda Viparita Dandāsana (two-legged inverted staff pose) in honor of beloved Guruji B.K.S. Iyengar, “Sundararājāsana”.  Join in the efforts here by signing the petition.

One must develop super-sensitive perception in the senses while practicing, so that one earns knowledge and wisdom in order to bring parity from the center into either side of the body. First of all, we must learn and adjust what we can both see and perceive in order to develop this quality of observation. For example, our eyes can perceive the front body and correct its movements. However the back body cannot be seen, but it is only felt and conceived by the mind, so it must be adjusted and corrected by the mind. The key to doing this is to balance the senses of perception with the senses of conceptions—the mind and the intelligence— so that they observe together the changes that take place while adjusting the various facets of the body.
This means the sādhaka [seeker] must use the fire of vision together with the fire of the intelligence of the mind to co-operate and co-ordinate, and, by utilizing the fire of the seer, to witness and correct whenever and wherever such corrections are needed. Such presentation establishes harmony, removing the disparities between the front, back and the right and left sides of the body, and the nerves, mind, intelligence and consciousness. By ‘nerves,’ I mean the prana or energy flows in the nervous system....
This way of practice diffuses the flame of the seer so that it radiates throughout the body.
— Yogācārya B.K.S. Iyengar, Core of the Yoga Sūtras, 2012.