http://gizmodo.com/why-mathematicians-are-hoarding-this-special-type-of-ja-1711008881
This spring, an 80-year-old Japanese chalk company went out of business.
Nobody, perhaps, was as sad to see the company go as mathematicians who
had become obsessed with Hagoromo Fulltouch Chalk, the so-called “Rolls
Royce of chalk.”
