A project initiated at Waseda University in 2023 is building a bilingual, searchable archive for Japan’s sangaku—mathematical tablets—and written records of tablets that have been lost. Its stated objective also includes sharp, scalable images.
The project reports roughly 900 surviving tablets scattered across Japan. Surviving sangaku are reported in more than three-quarters of Japan’s 47 prefectures, while the Archive map carries more than 1,000 pins marking tablet locations.
The project is presented as a cultural-preservation effort with potential uses in scholarship and teaching. The Archive and related materials are explicitly described as works in progress, so the project remains under development.
Making scattered objects searchable
Photography is one of the project’s central practical tasks. Most tablets lacked high-quality photographs in 2023, and obtaining them was described as a major archive task. The archive’s objective combines searchable records with sharp, scalable images.
Fieldwork involved obtaining publication permission from local caretakers and recording image-reuse conditions in the Archive’s metadata. Those conditions are recorded alongside the tablet information.
The described IIIF design pairs each image with searchable metadata, records core tablet descriptors and supports deep zooming. In that design, a visitor can inspect the image while using the associated information to search for the tablet.
The archive is not limited to objects that can still be photographed. Its stated scope includes written records of tablets that have been lost, extending the database beyond surviving images.
From the map to the mathematics
The archive also has a companion GeoGebra library. Its planned modules range from beginner-level problems with scaffolded hints to harder problems with solution discussions, alongside useful theorems.
The project presents these materials as a potential teaching use alongside potential uses in scholarship. The modules currently paired with the Archive represent only a tiny fraction of all sangaku problems.
Translation is another clear boundary: the Archive does not include translated problems for each tablet.
A historical record still taking shape
The archive’s historical material reaches beyond tablets that still survive. Its objective includes written records of lost tablets, and the Archive reports that more than a hundred tablets were hung during the Meiji period. The project places records of those lost objects alongside its surviving-tablet material.
The project is explicit about its present status. The Archive-related projects are described as works in progress, and the publication is a preprint identified in the front matter as arXiv:2608.25902v1 [math.HO], dated 26 Aug 2026, while the author-date line shows August 27, 2026.
The work reports partial support from the Rashkind Family Endowment during research conducted at the Waseda Institute for Advanced Study.
The paper provides direct URLs for the Sangaku Archive and its companion GeoGebra library. At its current stage, the described project includes searchable records, a location map, image viewing and selected geometry modules. Translated problems are not available for every tablet, the current GeoGebra modules cover only a tiny fraction of sangaku problems, and the work remains under development.
Paper data and sources
Original title: Introducing the Sangaku Archive
Authors: David Clark
Journal/Repository: arXiv
Status: Preprint, not yet peer-reviewed
First online: 2026-08-26
DOI: Not available
Original paper · Full text