The Sangaku lost from the Haguro Shrine in Murakami (Q2895284)

The mathematical votive tablet from the Haguro shrine studied in this article is not materially extant but the text of the problem engraved on its wooden surface has been preserved in several ancient wasan books from 1789 to the middle of the 19th century, approximately. Here, the authors first give a detailed presentation of these various sources (authors of the concerned mathematicians (such as Fujita Sadatsugu (1734--1804), Matsunaga Naohide (?--1850) and titles of the books in question with an elucidation of the schools of wasan they belong to, dates of edition, mainly). Then, they propound a full reconstruction of the tablet but without being able to restore with certainty the colours of its original geometrical drawing and the two dimensions (width and length) of its rectangular tablet. Lastly, the main part of the article is devoted to a very detailed mathematical derivation of the solution of the problem given in the tablet (length of the radius of a circle tangent to three other circles, the four circles being tangent to and inscribed in a same circle).