Is there a weight for a mathematical problem? The answer is Yes, if you talk about the Sangaku problem from the Edo period of Japan. Under the kind arrangement of Prof. Sonoda and Mr. Horibe during my visit to Nagoya this May (May 11, 2014), I was fortunate enough to see a few wooden Sangaku tablets, replica and original one, and really saw that mathematical problems can be really heavy. The next day after Horibe-San gave a workshop, Dr. Fukugawa Hidetoshi and I gave the other two talks in the Nagoya City University, we visited two temples in the Nagoya area.
Dr. Fukagawa is the premier authority on the Sangaku tablets in Japan. But he had a serious cold in that weekend, but still insisted to go with us to visit these places. In addition to him and me, we were also jointed with Mr. Horibe, Prof. Sonoda, one local high school math teacher to see these Sangaku wooden tablets.
The first temple we went is the Atsuta Shrine(Atsuta Jingu/熱田神宮). Right after we arrived, we were guided to a special room in the second floor by people from the Shrine, where the replica of two Sangaku tablets (dated 1841 and 1844, respectively) are carefully stored and not on display usually. Because we were special guests of Dr. Fukagawa, so we were lucky enough to have the privilege to examine these two beautifully-made replica.
After we had a brief lunch at Atsuta Shrine, Mr. Horibe brought us to a beautiful temple, Yourinzi temple (明星輪寺), in a nearby mountain area, Mount Ikeda (Ikeda-yama, 金生山) of Ogaki city, Gifu prefecture (岐阜縣大垣市). In this Buddhist temple, there is a well preserved Sangaku tablet made in 1865. Most importantly, many mathematicians and physicists, including Freeman Dyson, have been invited by Dr. Fukagawa to visit this temple to see the Sangaku tablet before.