In 1412 A.D., a ship carrying twelve people, reported to be residents of an island named "Yusanguk," landed at Koseong, and said that they had grown up on an island named "Mu-leung," where eleven families of sixty people lived. They then said they moved to "the main island," where they were now living. They gave the circumference of the main island and its north-south and east-west dimensions. (You can see the actual passage by viewing a previous post here.)
Since the people were described as coming from an island named Yusanguk, it seems logical to assume that "the main island" on which they said they were now living was named "Yusanguk," which is an obvious misspelling of the island "Usan-guk." Usan-guk was previously mentioned in documents of the Silla and Koryo kingdoms as being in the sea due east of Uljin. Also, since the people said they grew up on the island of Mu-leung and then moved to "the main island," we can surmise that Mu-leung was the smaller of the two islands. Moveover, based on the description they gave of the main island, we can surmise that they were referring to present-day Ulleungdo, and that Mu-leung was a smaller, neighboring island. This seems to have been the first mention of Ulleungdo having a neighboring island. The second mention was four years later in a passage from the Records of King Taejong, dated September 2, 1416.
In the above passage, Bak Seup gives a description of Mu-leungdo (Ulleungdo) based on information he heard while he was governor of Kangwon Province. Bak Seup's term as governor started in 1411, which means that the information he heard was probably pre-1411. Anyway, he said he heard that Mu-leungdo had a circumference of seven sik and a small, neighboring island. The small, neighboring island was most likely present-day Jukdo, which is Ulleungdo's largest neighboring island and less than four kilometers off its eastern shore. The information Bak Seup gives after that, however, is somewhat confusing. Is the information on the farmland and the path leading onto the island referring to Mu-leungdo (Ulleungdo) or to the small island? I think it is referring to the small island.
Source: 「太宗實錄」卷 三十二, 太宗 十六年 九月 庚寅條
September 2, 1416
庚寅/以金麟雨爲武陵等處安撫使。 戶曹參判朴習啓: “臣嘗爲江原道都觀察使, 聞武陵島周回七息, 傍有小島, 其田可五十餘結。 所入之路, 纔通一人, 不可竝行。 昔有方之用者率十五家入居, 時或假倭爲寇。 知其島者, 在三陟, 請使之往見。” 上可之, 乃召三陟人前萬戶金麟雨, 問武陵島事, 麟雨言: “三陟人李萬嘗往武陵而還, 詳知其島之事。” 卽召李萬。 麟雨又啓: “武陵島遙在海中, 人不相通, 故避軍役者, 或逃入焉。 若此島多接人, 則倭終必入寇, 因此而侵於江原道矣。” 上然之, 以麟雨爲武陵等處安撫使, 以萬爲伴人, 給兵船二隻、抄工二名、引海二名、火㷁火藥及糧, 往其島, 諭其頭目人以來。 賜麟雨及萬衣笠靴
김인우(金麟雨)를 무릉(武陵) 등지 안무사(安撫使)로 삼았다. 호조 참판(戶曹參判) 박습(朴習)이 아뢰기를,
“신이 일찍이 강원도 도관찰사(江原道都觀察使)로 있을 때에 들었는데, 무릉도(武陵島)의 주회(周回)가 7식(息)이고, 곁에 소도(小島)가 있고, 전지가 50여 결(結)이 되는데, 들어가는 길이 겨우 한 사람이 통행하고 나란히 가지는 못한다고 합니다. 옛날에 방지용(方之用)이란 자가 있어 15가(家)를 거느리고 입거(入居)하여 혹은 때로는 가왜(假倭)로서 도둑질을 하였다고 합니다. 그 섬을 아는 자가 삼척(三陟)에 있으니, 청컨대, 그 사람을 시켜서 가서 보게 하소서.” 하니, 임금이 옳다고 여기어 삼척 사람 전 만호(萬戶) 김인우(金麟雨)를 불러 무릉도의 일을 물었다. 김인우가 말하기를,
“삼척 사람 이만(李萬)이 일찍이 무릉(武陵)에 갔다가 돌아와서 그 섬의 일을 자세히 압니다.” 하니, 곧 이만을 불렀다. 김인우가 또 아뢰기를,
“무릉도가 멀리 바다 가운데에 있어 사람이 서로 통하지 못하기 때문에 군역(軍役)을 피하는 자가 혹 도망하여 들어갑니다. 만일 이 섬에 주접(住接)하는 사람이 많으면 왜적이 끝내는 반드시 들어와 도둑질하여, 이로 인하여 강원도를 침노할 것입니다.”하였다.
임금이 옳게 여기어 김인우를 무릉 등지 안무사로 삼고 이만(李萬)을 반인(伴人)으로 삼아, 병선(兵船) 2척, 초공(抄工) 2명, 인해(引海) 2명, 화통(火通)·화약(火藥)과 양식을 주어 그 섬에 가서 그 두목(頭目)에게 일러서 오게 하고, 김인우와 이만에게
Kim In-n was made Inspector of the Ulleungdo area.
Official (호조참판) Bak Seup said, "When I was governor of Kangwon Province, I heard that Mu-leungdo had a circumference of seven sik and had a small island next to it. It had fifty kyeol of farmland and a narrow entryway that only allowed people to travel single file; they could not walk two abreast. A long time ago a man named Bak Ji-yong lead fifteen families to the island and lived there. I also heard that they would sometimes conspire with Japanese pirates and steal. There is a man in Samcheok who knows that island. Please ask him to go there and check."
The king considered that good advice and called Samcheok resident and former military commander Kim In-u and asked him about Mu-leungdo.
Kim In-u said, "Samcheok resident Lee Man has been to Mu-leungdo and knows the details of the island." Lee Man was immediately sent for. Kim In-u added, "Mu-leungdo is far away in the middle of the sea, so there is not much contact with people there, which is probably why people flee to the island to escape military service. If there are many people living on the island, Japanese pirates will end up raiding it, and then use it to raid Kangwon Province.
The king agreed and made Kim In-u Inspector of the Ulleungdo area. He also made Lee Man his assistant and give them two troop ships, two ship's captains, two 引海 (인해), guns, gunpowder, and provisions. He told them to go to Ulleungdo, inform the leader there, and have them return. The king gave Kim In-u and Lee Man clothes, hats, and shoes.
The passage said that the island had fifty kyeol of farmland, and only one narrow path leading onto it. I am not sure how much fifty kyeol of farmland is, but there are several paths leading onto Ulleungdo while there is only one path leading onto present-day Jukdo. If the information about the farmland and the path were referring to the small island, then that means that the small island could not have possibly been Dokdo/Takeshima since Dokdo/Takeshima has no farmland or even soil to grow plants. It would also mean the fifteen families mentioned in the passage had been living on the small island. Nevertheless, Korean historians say that the "small island" mentioned in the passage was Dokdo/Takeshima, ignoring the fact that Jukdo is just offshore of Ulleungdo, and that Dokdo/Takeshima is ninety-two kilometers away and has no farmland.
The Mu-leungdo in the above passage is obviously referring to Ulleungdo, while the "small, neighboring island" seems to be referring to present-day Jukdo. This is different from the 1412 A.D. passage, which implied that Mu-leungdo was the smaller neighboring island. Since the 1412 description was direct testimony by former residents of the island and the 1416 information was hearsay, I would tend to believe the 1412 information, at least in regard to the name of the smaller island. Regardless of the name confusion, the 1416 passage does confirm that Chosun officials at the time knew that Ulleungdo had a neighboring island. Moreover, it seems to confirm the 1412 passage by suggesting that the neighboring island had farmland and inhabitants, which means the small, neighboring island could not have been Dokdo/Takeshima.