Maybe dropping back is a bit of a misnomer..it's more of an arching back with arms crossed and inhaling back up. I can't remember if I saw the floor today. Very weird disorienting feeling, as I have no idea where my body is in space. Prasarita C invokes a similar feeling for me, as I cannot judge where my hands are in relationship to the floor (closer than I think, though the floor could still be as far as the moon for all I can tell) while touching the floor (assisted) with my hands can feel super disorienting. First time gave me thoughts that I was touching the ceiling not the floor. With dropping back, it feels falling back. Except that my quads are already getting sore after 2 days. I could feel the connection (and more often, the lack of connection) of my feet to the floor.
In my feldenkrais training, much of what we do is work on the floor trying to feel where stuff is happening in our bodies, in space, and how the skeleton is affected by movement. What I have learned is that my brain likes to play tricks on me - movement of my shoulder blade downwards towards my feet can feel like it is the opposite direction or the leg that should feel longer actually feels shorter (this is apparently a common thing to feel). Learning to sit with the confusion about what you are sensing and feeling in your body (believe me, it's not obvious at all...) is a practice. My teachers say that confusion and anxiety feel similar to the nervous system, and that it is easy to replace confusion with anxiety, something I have definitely done over and over in this training and in my life.