Sometimes I play with the theory, what if Pattabhi Jois had come up with ALL the Ashtanga series, back when he had been offered the teaching job at the Sanskrit college. What if he had brought the yoga syllabus, the asana divided over four years (pretty much the list he gave to Nancy and David in 1973) and shown it to Krishnamacharya and that Krishnamacharya had used Jois' list for his 1941 book Yogasanagalu.
The theory falls down because although the Primary and Middle group in Krishnamacharya's book is almost exactly the same, especially the Primary group, as the Ashtanga we have now the Proficient group seems to be a catch all for a bunch of the more advanced postures.
It appears Pattabhi Jois organised the proficient asana into Advanced A or Advanced B. If Krishnamacharya had had an Advanced A and Advanced be list then surely he would have included it in Yogasanagalu as well or at least those under the title Proficient group would follow the general order that make up Jois' later series.
It begs the question whether Krishnamacharya ever intended the asana to be practised as fixed sequences (more on that later).
My guess is that the Primary group were probably pretty much practised in the order they are laid out in Yogasanagalu (depending on the time available, classes were supposed to be only an hour), as a kind of series and as one became more proficient the back bending sequence would be practiced and perhaps followed by the leg behind head sequence. And why not, if the student(s), Like Jois himself perhaps, were becoming more accomplished why not have them practice all the Middle group asana, the 2nd, Intermediate, series if you will.
And as for time, although Krishnamacharya writes of the long stays, the long slow breathing, the kumbhaka perhaps these were elements he might expect his students to practise themselves. Pedagogically, in the hour class, he may well have gone through the postures more quickly.
And Pattabhi Jois in the same situation as his teacher offering limited length classes may well have chosen to teach the asana with shorter stays although, according to Manju he would himself stay in certain asana for longer periods with longer, slower breathing.
Still no explanation as to why Kumbhaka (so prevalent in krishnamacharya's first book Yoga Makaranda 1934 written while the young pattabhi Jois was his student) was dropped.
This would suggest we have an
Ideal approach to asana IE. less Asana Longer stays, long slow inhalations and exhalations, perhaps kumbhaka
Pedagogic approach to asana IE. More asana, shorter stays, faster breathing.
When the Westerners came to practise , especially in the beginning at the Old, smaller, shala, they seem to have inhabited a middle ground. Because they were only staying for a number of months Pattabhi Jois seemed to be happy, even keen, to teach them as many asana as they wished and as they had nothing else to do all day they could have long classes and thus practice relatively slowly, so the breath perhaps a little longer and slower, more breaths in a posture.
As things changed and Ashtanga became popular, more and more coming to Mysore and students in the US and Europe to think of we ended up with the led class, full vinyasa dropped, less breaths in postures, breathing a little (or a lot ) quicker.
But what about that 3rd series, Advanced A, Krishnamacharya's Proficient group
Proficient group: In Yogasanagalu (1941) Krishnamacharya seems to have lumped together all the 'advanced' asana
Advanced A: Pattabhi Jois seems to have had an Advanced A and Advanced B list of postures for his four year Sanskrit college yoga course
3rd Series: in the 90s Advanced A seems to have been split into 3rd and 4th series Advanced B into 5th and 6th series we a few extra asana thrown in.
This has got me thinking though, can we see any broad outlines, mini groups of asana, subroutines in Krishnamacharya's list that suggest a rough outline of Pattabhi Jois' Advanced A sequence, his inspiration perhaps.