During the Northern Wei and Sui dynasties (386–618) experiments began with the construction of brick and stone pagodas. Even at the end of the Sui, however, wood was still the most common material. For example, Emperor Wen of the Sui Dynasty (reigned 581–604) once issued a decree for all counties and prefectures to build pagodas to a set of standard designs, however since they were all built of wood none have survived. Only the Songyue Pagoda has survived, a circular-based pagoda built out of stone in 523 AD.