Every thought has an image, form, dimension, weight, shape, colour, etc. Thought is as much matter as a piece of stone. A table is a mental image plus some external something. Whatever you see outside has a counterpart in the mind. The pupil is a small round thing in the eye and the retina is another small structure in the eye. How is it that the image of a big mountain, seen through that small aperture, is cast onto the mind? How does the big form of the mountain enter a tiny hole in the eye? This is a marvel of marvels. The image of the mountain already exists in the mind. The mind is like a big, vast sheet of canvas cloth that contains all the pictures of the objects seen outside.
Thought moves and passes from one man to another. Thought readily influences people. A man with strong thoughts can readily influence people with weak thought. Telepathy is a branch of occult science wherein the yogi can transmit messages to any man in any part of the world.
A thought of anger or hatred sends arrows from the mental factory towards the person aimed at. It harms the individual, sets up discord and disharmony in the thought world and comes back again to the sender and harms him also. If one can understand the effect and power of thought, he will be more careful in the manufacture of his thoughts in his mental laboratory.
Develop the faculty of producing only satvic (pure) thoughts by protracted mental discipline, dietetic adjustments, repetition of good hymns with meaning, good company, the study of divine books, japa (repetition of God's name), meditation, pranayama (yoga breathing), prayer, etc. A good man can help his friend, even though he lives a long way away, by good thoughts alone. Do not allow evil thoughts to enter your mental factory. Always watch your thoughts. Avoid useless thinking. Conserve your mental energy.
To cultivate sublime thoughts always keep yourself occupied in doing virtuous deeds and in the study of religious books. Destroy random thinking. Think of only one subject and its different aspects. When you do this never allow any other thought to enter the conscious mind. Again and again withdraw the mind to the subject on hand. Then take up another thought when you have exhausted the previous one.
By this practice you will develop organised thinking. The mental images will gain intense strength and force; they will become clear-cut and well defined. In ordinary persons the mental images are undefined.