"Tekagami" is a collection of dankan (fragmentary pieces of a writing) written in kohitsu (ancient calligraphy), which are stuck on a folding book made from thick papers. It is called this name as ancient calligraphy is easily appreciated. The name may also imply the look of opening mirrors because of its shape. It is written as '手鑑' or '手鏡' with the same reading.
After the Azuchi-Momoyama period, when ancient calligraphy came to be enjoyed for appreciation along with the popularity of Sado (Japanese tea ceremony), it became popular to cut out and collect a part of kansubon (books in scroll style) or sasshiso (books) such as scriptures, waka anthologies, and shosoku (letter) as 'kohitsugire' (samples of classical calligraphy). Tekagami is a book in which these pieces are placed together.
Fanciers of ancient calligraphy created tekagami by sticking kohitsugire on books to appreciate ancient calligraphy and excellent handwriting. Tekagami also became one of a brides' important household articles for samurai families and court nobles.
Experts on appraising ancient writing (such as Ryosa KOHITSU) called kohitsuka, kohitsumi, and simply kohitsu carried tekagami which contain representative kohitsugire stuck on hojo (copybook printed from the works of old masters of calligraphy) to be used as standards for appraisals. They used them as criteria for appraisals.
Kanbokujo' (Castle of Brush and Ink Album), 'Moshiogusa Album of Exemplary Calligraphy,' 'Companions of Past Ages,' and 'Otekagami' are national treasures.