How did yoga asanas originate?

Did Shiva really teach 8,400,000 asanas? How many asanas are there? How long is the list? The exact number of asanas is determined by who you ask! The history of yoga asanas on Wikipedia does a good job explaining the exact number of asanas within particular disciplines, giving various counts of 2, 4, 66 with 136 variations, 84, 908 with 1300 variations and the 8,400,000 Shiva list.