Headstand (Sirsasana) is often called the "king of poses" because of the many benefits it affords. It teaches balance and poise, increases the strength of the arms, positively affects the cardiovascular system, and allows, more than many poses, a few minutes for mental and physical stillness. It's a difficult pose, involving many precautions and prerequisites. Many Westerners feel that if they can practice Headstand, they are practicing "real" yoga.