Below is a map of Korea from a historical geography text entitled (新編標題纂圖寰瀛誌 - 신편표제찬도환영지). The map was supposedly originally made by Korean scholar Wui Baek-gyu (魏伯珪 - 위백규) in 1770 and was a part of his historical geography text "Hwanyeong-ji" (寰瀛誌 - 환영지), but this map was published by his grandson Wui Yeong-bok (魏榮馥 - 위영복) in a text entitled "Sinpyeon Pyoje Chando Hwanyeong-ji" (新編標題纂圖寰瀛誌 - 신편표제찬도환영지) in 1822.
The map shows an elongated Usando (于山島 - 우산도) drawn southeast of Ulleungdo, which a Korean professor HERE claims was "Dokdo" (Liancourt Rocks). Surprise! Surprise! However, by 1882, Usando was known to be Ulleungdo's neighboring island of Jukdo (竹島), which is a small island about 2.2 kilometers off Ulleungdo's east shore.
I am not sure why Ulleungdo and Usando were drawn the way they was, but since it was supposed to be a historical map, maybe Usando was drawn as large as it was to represent the old country of Usanguk (于山國 - 우산국), which was present-day Ulleungdo (鬱陵島 - 울릉도). It could not have been Dokdo (Liancourt Rocks) because it was drawn much too large and because Dokdo is essentially two islands, not one.