Sekka Zusetsu (雪華図説), translated as "Illustrated Diagrams of Snow Crystals," is a scientific text published in 1832 by Doi Toshitsura, the fourth daimyo of the Koga Domain during the late Edo period of Japan.
The publication is notable for being the first comprehensive study and categorization of snow crystals in Japan. Doi Toshitsura conducted his observations over approximately twenty years, utilizing a microscope—a tool introduced to Japan through Dutch trade. The original volume contains detailed sketches and descriptions of 86 different types of snow crystals, illustrating their characteristic hexagonal symmetry.
In 1840, Toshitsura published a supplement titled Zoku Sekka Zusetsu (Sequel to the Illustrated Diagrams of Snow Crystals), which added 97 further illustrations to the collection. The work was assisted by Toshitsura's retainer, Eagle (Kawabata) Zentaro, who helped with the observations and recording.
In addition to its scientific contributions, Sekka Zusetsu had a significant impact on Japanese aesthetics and design. The intricate patterns depicted in the book, known as Sekka-mon (snow flower patterns), became popular motifs for textiles, kimono, and various crafts during the mid-19th century. The study is regarded as a significant intersection of early modern Western scientific instruments and Japanese natural observation.
