Nagoya has a sweet by this name and so does Odawara, and both are made with rice flour, dense and cool and heavy on the tongue. Yamaguchi makes its version with bracken starch instead. The difference registers immediately. A toothpick passes through it without resistance, and the texture sits much closer to warabi mochi than to anything you would call a cake.

The method is short. Bean paste is worked together with bracken starch and a little wheat flour, then steamed in a cedar basket, and that is the entire process. The white one is the old form, said to have been first made by a shop in Yamaguchi during the Muromachi period. A dark one with brown sugar from Okinawa and a green one with matcha were added by later generations of the same family.

The name is borrowed. It belonged first to a medicine, a small black lozenge, and the sweet is thought to have taken it simply because the colour was similar. A confection named after a pill is not something anyone would invent on purpose.

It appears by name in the record of a banquet the Hagi domain laid on for the shogunate's inspectors in 1654, and there is an old rhyme about the lord of the Mori clan taking his tea with it. To eat one from a paper wrapper on a station platform, and to know it has been eaten here for more than three hundred and seventy years, is a small and slightly vertiginous feeling.