Calligraphy in six characters, In the red furnace, one snowflake

Items in the alcove (tokonoma)
The decorative alcove, or tokonoma, is a small yet important space in the tearoom as the objects arranged there set the theme or tone of a gathering. As with all utensils, the host usually takes great care in selecting what to place in the tokonoma and how to arrange it.
Often, we see a hanging scroll and a simple arrangement of flowers in a vase. An incense container in the tokonoma indicates to the guests that the host will not replenish the open hearth with charcoal during the gathering., The phrase “Above the red hearth, one flake of snow” (Koro jo itten no yuki) is an old Chinese saying used in the training of Zen Buddhist monks. It comes from the Chinese Chan (Zen) text The Blue Cliff Record (Chinese: Biyan lu, Japanese: Hekiganroku). The phrase—which is frequently used in the winter tearoom—suggests that an enlightened person is like a snowflake dancing above red-hot embers, unattached to illusions, vanishing instantly without a trace.
The calligraphy on this scroll is attributed to Matsudaira Sadanobu, lord of the Shirakawa domain. A daimyo lord of the mid-Edo period and a blood relation of the Tokugawa shoguns, Sadanobu was well known for his financial reforms. The name Shirakawa Rakuo (“old man of leisure”) was a moniker adopted after he retired, which helps us date this scroll.