The Spiritual Exercises of St. Ignatius of Loyola, (composed from 1522-1524) are a set of Christian meditations, prayers and mental exercises, divided into four thematic 'weeks' of variable length, designed to be carried out over a period of 28 to 30 days. They were composed with the intention of helping the retreatant to discern Jesus in his life, leading then to a personal commitment to follow him. Though the underlying spiritual outlook is Catholic, the exercises are often made nowadays by non-Catholics. The 'Spiritual Exercises' booklet was formally approved in 1548 by Paul III. (from wikipedia.com)