BPS books on meditation give qualified guidance in both the practical methods of meditation and the underlying theory. A thorough and informative survey is Amadeo Sole-Leris's "Tranquillity and Insight," which systematically explores both Samatha and Vipassanā meditation according to the classical sources and their modern adaptations. A modern classic is Nyanaponika Thera's "The Heart of Buddhist Meditation." Basic instructions in insight meditation are found in Mahasi Sayadaw's "Practical Insight Meditation", while Jack Kornfield's "Modern Buddhist Masters" collects tracts from a range of contemporary Theravada meditation masters from Burma and Thailand. A work with a unique flavour is "The Seven Stages of Purification" by the late Matara Sri Ñāṇanārāma Mahathera, one of Sri Lanka's most respected meditation masters of recent times.