The Science of Mind, by Ernest Shurtleff Holmes , at sacred-texts.com
Visualizing means mentally seeing the things that you wish to have or to do. When you mentally see the things you desire, and see them very clearly, you are presenting Universal Mind with images of thought; and, like the creative soil of the ground, It at once tends to project them into form. If the thought image is clear it provides a good mold; if it is imperfect the mold is a poor one. This does not mean that
one must set his mind or hold thought; it simply means that he must think clearly. There is no power in holding thoughts; indeed, the real secret of successful mental work is to loose thought and let Mind operate upon it.
The first thing to do is to decide what you wish to image into Mind. After having become composed in thought, begin to see the complete outcome of your desires, in mental pictures. Suppose that you wish to demonstrate a home; you should know just what kind of home you wish. Of course, if you simply thought of house you would get something, but the more definite the picture the better the results will be. In order to make the picture complete, decide just what kind of a home you wish to live in; then, in the silence of your thought, mentally look at this house; go from room to room, stopping here and there to look at some piece of furniture or at some picture on the wall. Make the whole thing real, as far as possible; enter the house, sit down and feel that you are actually living there, saying, "I am now living in this house." You have set a word in motion through the Law which will bring a realization of your desire, unless you, yourself, neutralize the picture by doubting it. Do this every day until the house appears. Use the same process in visualizing anything.
In order that you may fully understand just what I mean, I will illustrate by drawing a mental picture which I will ask you to follow as you read these lines. Imagine that you are with me; we will suppose that I am a man about six feet tall, with light hair and complexion. We are sitting on the front porch of a house that is painted green; it is a two-story house and sits quite far back from the road; there are tall trees standing in front of the house through which the sun is shining. We can see the little shadows as they play upon the porch through the open spaces between the trees. The breeze is gently blowing and the leaves are waving back and forth. I am talking to you, saying, "Let us take a walk together." We immediately rise from our seats, which are made of wicker, and walk down three stone steps to a gravel walk, leading to the street. As we go out through a stone gate we are suddenly met by a dog which is running along the street; he is a large, yellow dog, and is running rapidly. We watch him as he runs, barking,
down the street, till he turns a corner,--and our picture is at an end. Now, if you have carefully imaged each step in the above picture, you will understand what visualizing means.