The Chinese historical record the Books of Old Tang makes reference to ondol, saying: “In winter [Korean] people made themselves warm by making long hollows and supplied fire in them. ”
Hiina ajaloo raamat „Book of Old Tang ” viitab ondol’ile, öeldes:„ Talvel soojendasid [korealased] ruume, kuumutades pikki põrandaaluseid kanaleid. ”