Sai On
Turtleback tombs are thought to have been introduced into the Ryukyu Kingdom from Fujian in the late 17th or early 18th century ("in the interval between the careers of Shō Shōken and Sai On", according to Gregory Smits' monograph on the intellectual history of the Ryukyu Kingdom. Some authors give earlier dates; in particular, the tomb of Gosamaru (d. 1458) is often described as the first Ryūkyūan turtleback tomb. Okinawans believe that the shape of the tombs represent a woman's womb, so that the dead "return to the source".