St. Teresa of Avila (1515-1582) is considered one of the best of mystical writers and is a favorite of many, including me. She describes the journey a soul makes, through prayer, to union with God. Her three books, Book of Her Life, Way of Perfection, and Interior Castle, are all on contemplative prayer. In her book, Interior Castle, she uses the term mansions, and in Spain that is the title of the book, "Las Moradas" (The Mansions). She lists seven of them. The first three pertain to vocal prayer and meditation, the last four pertain to mystical prayer, what happens to the soul when God touches it. These last four are stages of contemplative prayer and the person praying has no control over these stages. In other words, he cannot do something to bring the effects about on his soul. People may have consolations in nature and they end in God, but spiritual consolations have their source in God and people enjoy them in a natural way [Interior Castle, p. 72-74].
In the seventh and innermost mansion dwells "the King of Glory, the greatest splendor. . . . The nearer one got to the center, the stronger was the light" [p.8]. The "mansion" is a person's soul and St. Teresa was given an image of it by Our Lord, as if it were a castle made like a diamond, in which there are many facets or rooms, just as in Heaven there are many mansions [p.28].
St. Teresa is different than most writers on contemplative prayer as she describes how one experiences contemplative prayer. The words, "stages", "levels", "grades", "mansions", should not be thought of as happening chronologically. Nor do people pass through them at the same speed. God sometimes will touch a person who is just a beginner with the higher level of contemplative prayer. Sometimes a person who prays a lot may never experience contemplative prayer. St. Teresa says the King does not give Himself to those who do not give themselves totally to Him - but rather to those who serve Him - those who do His will moment by moment, day after day [Thomas Dubay, Fire Within (San Francisco: Ignatius Press, 1989) 111ff.
Saint Teresa of Avil, Interior Castle, trans. E. Allison Peers (New York: Image Books, 1961).