This encyclopaedic work on Theravada Buddhism, "The Path of Purification", was written by Buddhaghosa.
The Visuddhimagga is a systematic examination and condensation of Buddhist doctrine and meditation technique. The various teachings of the Buddha found throughout the Pali canon are organized in a clear, comprehensive path leading to the final goal of nibbana, the state of complete purification. Thus the strict observance of Sila or morality is leading to the Purification of the body, the practise of Samadhi or concentration is leading to the Purity of the mind and the development of Panna or wisdom leading to perfect wisdom.
Originally composed in the fifth century, this new translation provides English speakers insights into this foundational text. In the course of this treatise full and detailed instructions are given on 40 subjects of meditation aimed at concentration, an elaborate account of Buddhist Abhidhamma philosophy, and explicit descriptions of the stages of insight culminating in final liberation.
Another version: Buddhaghosa. The Path of Purification (Vissudhimagga). Trans. Bhikkhu Ñāṇamoli. Kandy: Buddhist Publication Society, 2010. http://www.bps.lk/olib/bp/bp207h.pdf