Such a student may learn these texts by heart. Indeed, if one studies them seriously enough, one inevitably will. The Koan one is working at the time should become deeply embedded in one's mind. It can be the subject of zazen practice. Here, seated in the posture for meditation, the student repeats his koan to himself over and over again ... % ... The recitation is slow, and the inward voicing of each word or syllable may be done in phase with the slow, intermittent exhalation practiced in zazen. The koan infiltrates the mind. And it remains with the student not only when he is seated in formal zazen posture but at all times.
A. V. Grimstone, "Introduction" in Sekida, Two Zen Classics, pp16f