In Idle Talk on A Night Boat Hakuin sets forth this method of meditation that he claims cured his zen sickness and has supposedly long been reputed in Japan to have many health benefits. In Chinese medical terms, it's supposed to return the heart-fire to the tanden (or Ocean of Chi). Regardless of the merits of that understanding, I've found it to be a good relaxation method that I prefer to the more commonly encountered body-scan meditations.

When a student is training and meditating and finds that he has become exhausted in body and mind because the four constituent elements of his body are in disharmony, he should gird up his spirit and perform the following visualization:

Imagine that a lump of soft butter, pure in color and fragrance and the size and shape of a duck egg, is suddenly placed on the top of your head. Slowly it begins to melt, imparting an exquisite sensation as your head becomes moistened and saturated both within and without, It continues oozing down, moistening your shoulders, elbows, and chest, permeating your lungs, diaphragm, liver, stomach, and bowels, then continuing down the spine through the hips, plevis and buttocks.

At that point, all the congestions that have accumulated within the five organs and six viscera, all the aches and pains in the abdomen and other affected parts, will follow the mind as it sinks down into the lower body. You will hear this distinctly, like water trickling from a higher to a lower place. It will continue to flow down through the body, suffusing the legs with beneficial warmth, until it reaches the arches of the feet, where it stops.

The student should then repeat the contemplation. As the flow continues downward, it will slowly fill the lower region of the body and suffuse it with penetrating warmth, making him feel as if he is sitting immersed to his navel in a hot bath filled with a decoction of rare and fragrant medicinal herbs that have been gathered and infused by a skilled physician.

Inasmuch as all things are created by the mind, when you engage in this contemplation your nose will actually smell the marvelous scent of pure soft butter, your body will feel the exquisite sensation of its melting touch. Body and mind will be in perfect peace and harmony. You will feel better and enjoy greater health than you did as a youth of twenty or thirty. All the undesirable accumulations in your vital organs and viscera will melt away. Stomach and bowels will function perfectly. Before you know it, your skin will glow with health. If you continue to practice this contemplation unfalteringly, there is no illness that cannot be cured, no virtue that cannot be acquired,no level of sagehood that cannot be reached, no religious practice that cannot be mastered. Whether results appear swiftly or slowly depends only on how scrupulously you apply yourself.

Later in the work Hakuin mentions that many of his students affective illnesses have been cured by this method, and mentions a student who came to him in tears because he thought his illness was intractable until he tried this method and experienced a full recovery.

Waddell Notes:

Although Hakuin wrote it for his monastic community, the meditations it sets forth became popular and were used in secular circles as well. Prior to the discovery of Penicillin, many sufferers of tuberculosis in Japan used the techniques, apparently with some success, to judge from the large number of books promoting its benefits that appeared from the late nineteenth century up into the early post-war period.

Just a banal question (or not): in my current schedule I only have free time to practice meditation after diner. Immediately after. The question is: is that ok? Are there problems in practising zazen if I my belly is full, or is this really not recommended for some reason? Thanks for any help.