Today, most people think yoga means stretching on a mat. But the most famous book about yoga, the Yoga Sutras, barely talks about stretching at all.

The Yoga Sutras were written by a teacher named Patanjali, probably around two thousand years ago. A sutra is a short saying, like a thread of wisdom. Patanjali packed a whole system into 195 of them.

His very first definition is surprising. Yoga, he says, is calming the waves of the mind.

Picture a lake. When the wind blows, the water is choppy, and you can't see the bottom. When the wind stops and the water is still, you can see all the way down. Your mind is like that lake. Worries, wants and thoughts are the waves.

Patanjali says that when the mind becomes still, you can see your true Self clearly, like seeing the bottom of the lake.

So the postures are helpful, but they are only one part. They prepare the body to sit still so the mind can calm down. The real goal of yoga is a quiet, clear mind.