Bhekasana (Frog Pose), also known as Mandukasana, registers as 4* on the scale of difficulty. This pose is quite challenging for me and, as you can see, I have quite a ways to go before I find the physical depth of the pose that Iyengar demonstrates.
If, like me, you find yourself having difficulty practicing the full version of Bhekasana, start by exploring Eka Pada Bhekasana, or one-sided Frog Pose. To practice this variation, lay on your belly with legs extended. Place your left forearm on the floor in front of you, parallel to the mat. Then bend your right knee and reach your hand onto your right foot, rotating your hand so that your wrist is facing backward and your knuckles face forward. This variation will allow you more freedom in your torso and will give you the opportunity to carefully explore the pose on each side before attempting the full asana.