In which scripture (not of Kaliyuga), Surya Namaskara (12 steps asana) is mentioned? I have checked Hatha yoga Pradipika and Yoga Sutras of Patanjali, but nowhere Surya Namaskara is mentioned.
I have found a related question What is the origin of twelve Surya namaskar mantra? which asks for the origin of the mantras chanted during the asana but it doesn't ask about the origin of the asanas. I also doubt the so called surya namaskar mantras. They are just Surya mantras, nowhere it is mentioned that it is related to Suryanamaskar-12 Yoga Poses. Moreover Sun or Surya God have 1000 names or name mantras.