Full-Touch

“I have a large cache of the original Japanese Hagoromo Full-Touch chalk - God's own chalk, the Rolls Royce of chalk, the chalk that prevents its wielder from making a mistake - which I use in those increasingly rare times I have access to a chalkboard.”

“At the chalkboard, I use only Hagoromo faru ta'chi ("Full-Touch") chalk, for which it has been claimed that it is impossible to make a mathematical mistake when writing with this chalk.”