From a talk by Zen Master Seung Sahn, 1977:
I often talk about primary point. What is primary point? When you have a
scale and there is nothing being weighed, the indicator points to zero. You put
something on it, and the pointer swings to "one pound." You take it off, the
pointer goes back to zero. This is primary point. After you find your primary
point, then good feelings come, bad feelings come, so your pointer swings in
one direction or the other. But this doesn't matter. Don't check it. When the
feeling is over with, the pointer swings back to zero.
But if you haven't found your primary point, then it is like taking a heavy
object off of the scale and having the pointer stay at "ten pounds." Or the
pointer moves back only part-way, it doesn't go completely back to zero. Then
you have a problem. Your scale does not weigh correctly. Maybe if you put a
heavy object on it, it will break completely.
So first you must find your primary point. Then you must keep it very
strongly.
A taxi has weak shock absorbers, so it hits a small bump and bounces up and
down. A train has strong shock absorbers, so it is very steady. If you keep your
primary point, your mind-spring will become stronger and stronger. You will
meet big problems and your mind will move less and less. A big problem
comes, your mind moves, but soon returns to primary point. Finally your
mind will be very strong; it will be able to carry any load. Then saving all
people is possible.