This is an awesome video of one of the most renowned yoga teachers in the world. BKS Iyengar, now 87 started the iyengar form of classic yoga and have been teaching and practicing the same for 70 years. 

This video shows him in his younger days perfoming some of the most difficult yoga poses.

Will write more about this - tell then just watch and wonder. Its just amazing - the precision, the flexibility and the concentration. looks unreal, but with dedication and practice, its achievable