For presence of mind, increase in eagerness and improvement of memory the exercise known as Paas Anfaas is most efficacious while it is the simplest of exercises (ashghaal). This exercise is a breathing exercise and its method is as follows:
Take a deep breadth. While inhaling concentrate on the word اَلله. Exhale vigorously. While exhaling concentrate on هُوْ. Do this repeatedly.
In the beginning practise this exercise in solitude and do it until one feels a warm sensation. Thereafter, this exercise should be carried out at all times while walking, sitting, etc. In all states endeavour to establish this concentration. In the beginning some effort is required. However, after a short while one’s breathing will be so conditioned that it (the breathing) will be along this pattern without one consciously resorting to it.