Of the forty-two devoted to the 'perfection of Wisdom', the Diamond and the Heart Sutras have for centuries been considered the holiest. The Prajnaparamita texts, as the Buddhists Wisdom Books are called, were composed in India between 100 B.C. and 600 A.D. (the Diamond and Heart Sutras probably about the fourth century) and became popular throughout Tibet, Mongolia, China and Japan. Dozens of translations have been attempted, but the famous Buddhist scholar Edward Conze, who studied the Prajnaparamita for more than thirty years, was the first to explain the sutras in a manner intelligible to Western readers.