*Gomei sanpo* (1826) was a collection of *sangaku* problems attributed to the mathematician Iesaki Yoshiyuki and assembled by publisher Osakaya Mokichi. This is the title page of the book.

Imaginative problem situations involving fitting circles into fans, i.e. circle-packing in fan-shaped regions:

More typical problems involving circle packing and stacking:

For another set of *sangaku* problems, see Mathematical Treasure: Japanese Temple Mathematics, by Frank J. Swetz, here in *Convergence*.

*These images are presented through the kind cooperation of the National Diet Library, Japan, and are used with permission. They were obtained from the library’s digital gallery exhibit, Japanese Mathematics in the Edo Period, where a complete examination and viewing of the item presented above can be found. *