Why the World’s Best Mathematicians Are Hoarding Chalk – YouTube

Once upon a time, not long ago, the math world fell in love … with a chalk. But not just any chalk! This was Hagoromo: a Japanese brand so smooth, so perfect that some wondered if it was made from the tears of angels. Pencils down, please, as we tell the tale of a writing implement so irreplaceable, professors stockpiled it.

So many people sent this to me. For good reason, it’s fascinating and wonderful.