The image at the door
The Encyclopedia of Korean Culture, published by the Academy of Korean Studies, notes that the Samguk Yusa records Cheoyong’s image hung at the door. It is the earliest record in our sources for the Korean charms that were later written on paper.
To verify: The date of the Samguk Yusa and the exact passage, from a published translation; What the Samguk Yusa says about why Cheoyong’s image was hung