Origami is the art of paper-folding. Its name derives from Japanese words ori ("folding") and kami ("paper"). Traditional origami consists of folding a single sheet of square paper (often with a colored side) into a sculpture without cutting, gluing, taping, or even marking it. Distinct paper folding traditions arose in Europe, China, and Japan which have been well-documented by historians. These seem to have been mostly separate traditions, until the 20th century. In China, traditional funerals often include the burning of folded paper, most often representations of gold nuggets (yuanboa). The practice of burning paper representations instead of full-scale wood or clay replicas dates from the Song Dynasty (905–1125 CE), though it's not clear how much folding was involved. In Japan, the earliest unambiguous reference to a paper model is in a short poem by Ihara Saikaku in 1680 which mentions a traditional butterfly design used during Shinto weddings. Folding filled some ceremonial functions in Edo period Japanese culture; noshi were attached to gifts, much like Greeting cards are used today.