Dhyaya or meditation is in the keeping up of the flow of one idea with a continuity as unbroken as the flow of oil. Meditation is of two kinds, viz, concrete and abstract. If you meditate on any picture or concrete object it is concrete meditation. If you meditate on an abstract idea, on any quality such as mercy, tolerance, it is abstract meditation. A beginner should practise concrete meditation. For some aspirants, abstract meditation is more easy than concrete meditation.
There is a realm where there is neither earth nor water, neither space nor time, neither perception nor thinking, neither light nor darkness, neither east nor west. That is the abode of Brahman where there is everlasting peace and bliss.