A meditator who always sees others but not himself is following a hopeless mental exercise. One must concentrate on one’s own heart and mind and penetrate deeper into them. If one only looks superficially, one will not understand one’s own mind.
So the purpose of (useful) mental exercise is to see oneself. To see what? … To see corporeality (Rupa ), feeling (Vedana ), perception (Sanya ), intentional activities (Sankhara ), and consciousness (Vinnyana). To See mind and matter (Nama rupa) (through developing Citta ), mental factors (Cetasika ), form or matter (Rupa ) and, finally, Ultimate release (Nibbana ). Then one can see feeling, mind and Dhamma. Concentrate on the body while walking, lying down, sitting, defecating, urinating. Even breath is included in body (Kaya).
There is not much to practising Samadhi. Just keep on working until the mind is peaceful. Do not expect to have different visions. Do not ask “Why do I see nothing after such a long period of meditation practice when others say that they “see ” different things. Do not think in that way because each person has his or her own result, virtue and happiness.
So after realizing that there are different individual accumulations, we are contented with our own way and, at least, we are not full of restlessness.