Celadon pillows pierced with a hole at both ends seem to be related to the phrase “the holes pierced on either side of pillows made of
ceramics are a passageway for dreams” in Zhenzhongji (枕中記, The World Inside a Pillow), a novel written in China during the Tang dynasty. Celadon pillows are also described as a medium for entering the ideal world in a poem by the Goryeo-era writer Yi Gyu-bo.