The Jomon through Yayoi people used a unique Y-shaped shura which allowed them to transport heavy and large items such as timbers, trees or megalithic stone.
OZAWA, Yasumi Usage of Y-Shaped Lumber of Excavations in Sakuramachi-Site (The positioning of Y-shaped lumber in the history of sledges in Japan) Nihon Kikai Gakkai Nenji Taikai Koen Ronbunshu,VOL.2006;NO.Vol.5;PAGE.369-370(2006)
They had also developed a sophisticated technology involving a Y-shaped shura used for transporting heavy and/or large items such as timbers, trees or megalithic stone. Abstract: The Y-shaped lumbers of the chestnut trees were excavated at the Sakuramachi-Site in Oyabe City, Toyama, Japan in 1997. It is thought that the people of the Jomon period about 4000 years ago used the Y-shaped lumbers to transport heavy items such as giant trees. The positioning of Y-shaped lumbers in the history of sledges in Japan is discussed in this paper. The Y-shaped lumbers of the Sakuramachi-Site were compared with sledges excavated in Kitoragawa-Site of the Yayoi period in Higashiosaka City, Osaka Prefecture, Japan. It was confirmed that the Y-shaped lumbers of the Sakuramachi-Site is the oldest Shura in the world for the transportation of giant trees under the assumption that the Y-shaped lumbers at the Sakuramachi-Site are Shura