Day 21 is Mountain pose or Tadasana.
Tadasana is really the foundation to all yoga poses. You always bring a bit of this pose into any other pose you do. It looks easy. It’s just standing right? Not exactly. Yoga Journal says to start with your feet together, big toes touching, but I usually have my feet a little bit apart because it feels more stable to me. Your thighs should be firm. A common cue for that is “lift your knee caps.” There should be a line of energy from your arches to your groin so your pelvis is engaged here with your tailbone pointing toward the floor. Press the shoulder blades together onto the back, but don’t let your sternum and ribs flair out. Ears should be over your shoulders which are over your pelvis which are over your ankles. Got all that? Then you’re in Mountain pose.