Meditation exercise (Lama Drati): Imagine a white dot in centre of forehead and keep attention held unmovingly on it for one hour. Or you can place it in heart. Better still, imagine the figure of Buddha projected in front of you, radiating white light. Or place the Buddha miniature-sized on your head. All these are called exercises to attain one-pointed mind. Only after this attainment can you properly do the more advanced exercises.
-- Notebooks Category 4: Elementary Meditation > Chapter 3: Fundamentals > # 141