Technically this is a Forum archive because I archived it a long time ago when I first met my friend Dave Meikle. He sent me the following as a training excercise for San Ti Shi.

A part of Xingyi that is often neglected is the mind part of it. After all, it is called Form-Mind Boxing. Each movement should backed up with a strong mental picture of your movements moving with tremendous power, stiking through your target and off towards the horizon line. The following is Meikle's exercise for the mind while in San Ti Shi, the mother of Xingyiquan.

SAN TI SHI - the action of Splitting
Stand with front knee over heel, lead hand along center shoulders relaxed (allowing the elbows to drop inward) and second hand beside lead elbow. Second hand can be open or closed, depending on your school, or whatever you feel like 'expressing'. Generally the closed fist (heart) is a Phoenix eye, and an open palm can be either thumb and 4 fingers flat (as if on a table) and slightly open (cotton balls) or thumb underneath fingers, as if holding a small steel ball.
Feel your body sinking into the posture, as if you are continually sinking and never quite being able to 'arrive' in that posture. Imagine a 1000 lb. Steel ball suspended from a chain off you tail bone into the center of the earth, and allow the feeling if downward pull to go through your legs from the sheer weight of it. Attach a string to the crown of your skull (bai hui point) and have it pull upward, the combined effect with the steel ball will elongate the spine and open meridians. Another analogy for bai hui is to imagine a 'meat hook' in the back of your skull pulling up, or to imagine a 'push button' for a light above your head, and your have to push up on the button to keep a light on.

Feel the skin from your elbows to your fingers getting heavy. All the weight in your arms and body is sinking into earth. The skin on your arms (elbow to finger) is starting to sag from its weight, and eventually hangs tattered off the bone. Feel the sinking in the bones as the body continues to 'fall' into this posture. Maintain this for a few minutes.

Between your fingers imagine there is cotton balls. Experience the feeling of them and embrace them with your fingers, but don't 'flatten' them, they are delicate. Feel the weight of a steel ball in each open hand; allow the weight to flow evenly through to the elbows, creating a balanced heaviness throughout the arm. Try to 'feed' the lead hand forward, as if pushing the steel ball through extremely thick mud, simultaneously drawing the reverse hand back. Feel the connect wrap around the body and through the spine and into the legs. This is the action of split (reverse, opening) and the element of metal (sinking, condensing).