Nanso and naikan are useful. Just a few remarks.
Yasenkanna does mention visit of young and very sick Hakuin at the cave of Hakuyushi. As one can slowly read through the text Hakuyushi first checked pulses etc. In fact in Japan this meditation is applied together with checking pulses and body/eneregy/mind condition. Actually the practice itself was secret and Yasenkanna mentions it, but does not go into details.
Practices like this I guess?
(Extract from http://www.leggett.co.uk/books/szr.htm
Leggett: A second Zen reader. The Tiger's Cave and Translations of Other Zen Writings. Charles E. Tuttle, Tokyo 1988)
I said : May I hear of the use of the So cream?
Hakuyu said : If the student finds in his meditation that the four great elements are out of harmony and body and mind are fatigued, he should rouse himself and make this meditation. Let him visualize placed on the crown of his head, that celestial So ointment, about as much as a duck's egg, pure in colour and fragrance.
Let him feel its exquisite essence and flavour, melting and filtering down through his head, its flow permeating downwards, slowly laving the shoulders and elbows, the sides of the breast and within the chest, the lungs, liver, stomach and internal organs, the back and spine and hip bones. All the old ailments and adhesions and pains in the five organs and six auxiliaries follow the mind downwards. There is a sound as of the trickling of water. Percolating through the whole body, the flow goes gently down the legs, stopping at the soles of the feet.
Then let him make this meditation: that the elixir, having permeated and filtered down through him, in abundance fills up the lower half of his body. It becomes warm, and he is saturated in it. Just as a skilful physician collects herbs of rare fragrance and puts them in a pan to simmer, so the student finds that from the navel down he is simmering in the So elixir. When this meditation is being done, there will be psychological experiences, of a sudden indescribable fragrance at the nose-tip, of a gentle and exquisite sensation in the body. Mind and body become harmonized, and far surpass their condition at the peak of youth. Adhesions and obstructions are cleared away, the organs are tranquillized and insensibly the skin will begin to glow. If the practice is carried on without relapse, what illness will not be healed, what power will not be acquired, what perfection will not be attained, what Way will not be fulfilled? The arrival of the result depends only on how the student performs the practices.
Thanks for the replies all