Polishing a tile into a mirror is a famous Zen story.
Mazu Daoyi left home at 12 years of age and became a student of Zen master Nanyue Huaizang. When he started to practice Zen Buddhism, he usually sat in meditation all day long. One day Nanyue Huaizang came to see him. When he saw Daoyi meditating he asked, “Why are you sitting in meditation?” Daoyi said, “To become a Buddha.” Master Huaizang took hold of a piece of tile and began rubbing it. Daoyi asked Huaizang “What are you rubbing the tile for master?” “I want to polish it into a mirror.” Huaizang answered. Daoyi felt puzzled. He asked, “How can you hope to polish a piece of tile into a mirror?” Huaizang replied, “Since a piece of tile can’t be polished into a mirror, how can simply practicing sitting meditation make you become a Buddha?”
“What must I do then to attain Buddhahood?” Daoyi asked. But Huaizang countered with a question, “Take the case of an ox-cart. If the cart doesn’t move, do you whip the cart or do you whip the ox?” Daoyi didn’t know how to answer so he just kept quiet. Huaizang continued, “In learning sitting meditation, do you aspire to learn sitting Zen, or do you aspire to imitate the sitting Buddha? If the former, Zen doesn’t consist in sitting or lying down. If the latter you must know the Buddha has no fixed postures.” Huaizang kept talk to Daoyi, “The dharma goes on forever and never abides in anything. You most not therefore be attached to or abandon any particular phase of it. To sit with the purpose of becoming a Buddha is to kill the Buddha. To be attached to the sitting posture is to fail to comprehend the essential principle.” After listened to Huaizang, Daoyi realized that just practice sitting in meditation is a wrong way to reach enlightenment. This is because Buddhahood is the great clarity of enlightenment; it is not dependent on practicing physical postures. Mazu Daoyi served Huaizang for ten years and eventually became awakened.

When I started to practice Tai Chi Chu’an 23 years ago I felt it’s just like practicing Zen. I didn’t know how to set about practice because it goes against most Martial art principles. You shouldn’t use any physical strength and you must go slow and relax. I wanted to know “If you don’t use any physical strength then how can you use Fa Jing?” I also found I couldn’t relax; after bending my knees for over thirty minutes my legs started to shake. And I was told that if you want to relax your body you have to relax your mind too. What could I do? I just followed what my teacher said and kept practicing until one day my body and mind naturally began to work together. It is a process for which there is no substitute.