Oliver Heywood, Heart Treasure, pp. 250-252:

Among the directions for maintaining and promoting religion in the soul, the practice of devout meditation should hold a prominent place. Yet, as this topic is of large extent, and specially important, I have deemed it most proper to give it a separate consideration. In presenting it, I shall set before you some of the most appropriate subjects of meditation; and then show the influence of such meditation in preserving and invigorating holy affections.

Christian meditation is the contemplative and earnest fixing of the mind on the great spiritual realities which the Bible has revealed to us. It should be connected with prayer and the study of Scripture, to awaken and inspire it, and to furnish it with suitable themes; yet it differs from both. Prayer is the converse of the soul with God; the direct outpouring of its wants and desires before the throne of Infinite Mercy. The reading of Scripture is the exercise by which the soul seeks to learn God's will, and to gather in the communications which He has made of His character and purposes. But meditation is the soul's conference with itself; the discourse which it holds with truth obtained, and impressions received, in the secret sanctuary of its own consciousness. It is not simple revery or aimless speculation; nor is it a mere effort of the memory to recall and treasure up religious instruction. It is the set and solemn endeavor of the soul to bring home to itself divine things; and so to resolve, ponder, and digest them, as to work their transforming power into every element and faculty of its being. The subjects of thought best suited to such an exercise will now be laid before you. You are not, however, to suppose, that the entire enumeration is to occupy you at any one time. This is not practicable, and would not be the most judicious method, if it were. In order that you may derive the fullest benefit from meditation, it should be engaged in at regular intervals, either immediately before or after your seasons of private devotion; and, at each of these periods, you will find it most useful to employ yourself particularly on some one department of truth, provided you do not view it as isolated, but in its broad and comprehensive relations to the whole system of truth. Thus traverse successively the different portions of the vast field of Divine Revelation, until its entire compass shall have been brought within the scope of your contemplations.