The following will take place on Sunday, August 31:
"Repeat and become steady in your daily practices. Those who find it difficult to master all these asanas within this period can continue with them for several more weeks."
We have arrived at another juncture. Week Thirteen is one of the three times (the others are Week Seven and Week Eighteen) in which the sequence takes a kind of break. Rather than stating an explicit set of poses to practice, Iyengar instructs us to spend the week reflecting upon and assessing what has taken place thus far. It's a reminder to be (among other things) aware, honest, and patient. What are you doing? Are you doing it well? Don't hurry. It is not an accident that we have been exposed to this particular set of asana to this point -- their success is an imperative foundation for moving forward. He is emphasizing the importance of mastering these poses because the coming weeks are going to include more challenges. Soon we will see the first of the back-bending poses, more seated folds and twists, and more inversions. If the current set of asana are not yet performed skilfully, then the new poses are possibly/probably not an appropriate addition. And notice that he very clearly provides permission to take as much time as is needed before moving on.
How do you know if a pose has been "mastered"? How do you know if you and your practice are ready for something new? Answering those questions is, in fact, part of the practice; that is part of what we are learning while on the mat. There are both objective and subjective elements to analyze, and they aren't always easy to discern. But in short, to call a pose "mastered" means that you fully grasp its form and its function -- what it is, how to do it, and why. It means that you can, with reasonable ease and comfort, enter, hold, and exit the pose. It means that transitions are smooth, and that something very closely resembling the traditional "full form" is accessible. It means that lots of detailed instructions are no longer necessary because the body's positioning is well-known and comes about naturally. It means that the breath is consistently steady before, during, and after the pose. And it likely means that you are no longer regularly experiencing distinct and measurable improvements.
It does not mean that the pose has entirely lost its challenge. It definitely does not mean that there is nothing left to learn from it. And it doesn't necessarily have anything to do with whether or not you continue to use some kind of prop(s). It has more to do with an internal shift of control. By that I mean that when a pose is brand new and very challenging, it is your body (your flesh and bones and muscles) which is in control and decides how well and for how long you can be in it. But when a pose has been mastered, it is your "something-more" (your spirit/soul/will/heart/essence/etc.) which controls the experience. How well and for how long becomes a pursuit of mindfulness, curiosity, patience, and passion rather than physicalness. It becomes a matter of want to rather than have to. And it's a recognition of internal rather than only external sensitivities.
Patanjali says very little in regards to asana, but one thing he does say is "Sthira sukham asanam," which is often translated as something like "Poses must embody steadiness (sthira) and ease (sukha)" (Sutra II.46). Iyengar elaborates on this by saying that "Asana is firmness of body, steadiness of intelligence and benevolence of spirit" (Light on Yoga Sutras). In some ways those are incremental experiences: first, firmness of body; then, steadiness of intelligence; and finally, benevolence of spirit. And in other ways they are all simultaneously necessary. Further discussion of this Sutra can be saved for another time. The point is that asana are about much more than just strength and flexibility. They are about the body, and they are about something more than the body. We already know that. But what we might still need to better understand is how to acknowledge when it's about the body, when it's about something more than the body, and when it's both. Week Thirteen is an opportunity to practice that.
In class on Sunday, we will, once more, practice the Weeks 11 and 12 Sequence with an emphasis on assessing which components are necessary for a "masterful" pose.
Sanskrit names are in bold.
(English names are in parentheses.)
[Numbers in brackets correspond with illustrations.]
Poses with an * are new to the sequence.
NOTICE THE CHANGE IN THE ORDER OF POSES
Utthita Trikonasana (Extended Triangle pose) [4 and 5]
Parivrtta Trikonasana (Revolved Triangle pose) [6 and 7]
Utthita Parsvakonasna (Extended Side-angle pose) [8 and 9]
Parivrtta Parsvakonasana (Revolved Side-angle pose) [10 and 11]
Virabhadrasana I (Warrior pose first variation) 
Virabhadrasana II (Warrior pose second variation) 
Virabhadrasana III (Warrior pose third variation) 
Ardha Chandrasana (Half Moon pose) 
Parsvottanasana (Intense Side-stretch pose) 
Prasarita Padottanasana I and II (Standing Wide-angle forward bend first and second variations) [33 and 34, 35 and 36]
*Padangusthasana (Standing Big-toe pose) 
*Padahastasana (Hand-under-foot pose) 
*Uttanasana (Standing forward bend) 
Parighasana (Gate pose) 
Urdhva Prasarita Padasana (Upward Extended Legs pose, aka UPP) [276 to 279]
Paripurna Navasana (Full Boat pose) 
Ardha Navasana (Half Boat pose) 
Salamba Sarvangasana I (Supported Shoulderstand first variation) 
Halasana (Plow pose) 
Karnapidasana (Ear-pressing pose) 
Ekapada Sarvangasana (One-legged Shoulderstand) 
Jathara Parivartanasana (Revolved Abdomen pose) [274 and 275]
Ujjayi Pranayama with inhalation retention (Section 203) in Savasana