# Kan Chu Sen's Wakoku Chiyekurabe

The first published reference to folding and cutting of which we are aware is
a Japanese book, *Wakoku Chiyekurabe* (Mathematical Contests), by Kan Chu
Sen, published in 1721. This book contains a variety of problems for testing
mathematical intelligence. One of the problems asks to fold a rectangular
piece of paper flat and make one complete straight cut, so as to make a typical
Japanese crest called sangaibisi, which translates to ``three folded
rhombics.'' The author gives a solution that consists of a sequence of simple
folds, each of which folds along a line.
Many thanks are due to Gisaku Nakamura for providing us with the
reference, a copy of the book, and translation of the title and relevant
contents.
Here are scanned images of the relevant pages in the book: