During yongmaeng chôngjin, the monks in meditation hall do not sleep for seven
straight days, breaking from their practice only for meals. They even skip the
dinner ritual in the main Buddha hall so as to devote themselves completely to their
meditation. In this intensive period, the monks face one another in two separate
rows down the middle of the meditation hall, rather than facing away as they
usually do. ... Otherwise the meditation sessions take place pretty much as
always, with fifty-minute sitting periods followed by ten minutes of walking. But if
the succentor feels people are tiring, he might quicken the pace to twenty-five
minutes sitting followed by five minutes walking, walk for longer periods, or try
any number of other stratagems to keep his charges vibrant (or at least awake).
Other than its obvious interminableness, the major difference between
yongmaeng chôngjin and regular meditation periods is that the large warning stick
(changgun chukpi) is in use constantly throughout each sitting period....
If the drowsy monk does not react to the guard's presence, the guard taps
him on the shoulder with the stick and gives him one round of blows.
As grueling as yongmaeng chôngjin might seem to the uninitiated, its purpose is
not to torture the monks. Rather it provides an incredibly intense, but still carefully
controlled, environment in which to meditate. The hope is that several days of
sleeplessness will apply enough pressure on the meditators that they will be able to
have a genuine breakthrough into their meditation topics, or hwadu ("critical
phrase" [of a Koan, such as "MU"]). Just before yongmaeng chôngjin begins, the Son master tries to impress
upon the meditators that the only way they will be able to survive the week is to
remain concentrated at all times on their hwadu and to arouse the sensation of
doubt. From my own experience, the sheer enormity of the task of remaining
awake for seven straight days was enough to frighten me into focussing on the
hwadu, as if I were clinging to it for dear life. The instant the mind wavers, you are
bludgeoned by bone-numbing fatigue, so the only hope you have of getting through
the week is to maintain your concentration.
... I remember several times being
totally confused as to whether the guard carrying the stick was actually
hitting me, or whether I was dreaming the whole thing. During walking
meditation I might as well have been walking in space, so ungrounded
and amorphous did I feel. I was not alone in that. During one walking
session, one of the other monks fell asleep while rounding the corner of
the room and walked straight through one of the wood-and-paper doors
along the side of the hall. He was rudely awakened as he toppled onto the
wooden veranda outside. At the end of the retreat when we were finally
allowed to sleep, I collapsed at my seat, utterly exhausted. Although we
were supposed to awaken at three in the morning to begin anew our reg- ular meditation schedule, I could not be roused. The monks left me laid out on my cushion and sat and walked around me. It was not until just
before the late-morning meditation period began at eight that I finally
awoke. Fortunately, in subsequent retreats my practice had matured to the point where I could maintain extended periods of concentration on
the hwadu. Then it really was quite remarkable how effective—even al- most refreshing, in a bizarre sort of way—such intensive practice could
be.
https://terebess.hu/zen/mesterek/buswell-experience.pdf