One of his maps was mentioned in an 1876 letter entitled "Concerning Matsushma 2," which was written by Watanabe Kouki (渡辺洪基), the Director of the Bureau of Documents in Japan's Ministry of Foreign Affairs at the time. In the letter, Mr. Watanabe said that Toda Takayoshi's survey map showed the circumference of "Takeshima" (Ulleungdo) to be about 23 ri, a measure that was calculated by adding up all the measurements of the ins and outs of the shoreline on the map. He also said the island in the south corner of the map was probably Uindo (于人島), which was very probably a misspelling of Usando (于山島).
The reference to the map in Mr. Watanabe's letter was as follows:
Moreover, it you add up all the measurements done by Toda Takayoshi (戶田敬義) on his map they total about 23 ri. (That includes all the ins and outs of the shoreline.) That circumference is more than just a little different than that of Matsushima, or Dagelet. On the south corner of the map is drawn an island that has a circumference of about 1.5 ri. The island is probably Uindo (于人島).