Mountain :: Tadasana
This is simply a pose of poise. It is a restful pose, but it is not without concentration and alignment. The pose consists of standing erect with your feet together and aligning your body so that your ears are above your shoulders, which are above your hips which are above your feet. Take care that your stomach is in, your chest is forward and your spine is stretched up with the neck straight. Tighten your legs to pull your kneecaps up your thighs and contract the buttocks to pull the muscles up at the back of your thighs.
Shift your body weight around until you find the sweet spot in your feet where you are not bearing the weight of your body either on the heels or the toes, but distributed evenly throughout the foot.
Your arms can be at your sides, as shown here, or stretched up overhead.
This pose is indespensible for learning the simple act of standing correctly. A healthy body is one that can stand in poise with ease. Practice the mountain pose to achieve this.