"Yoshida Koyu"(1598-1672) (or "Yoshida Mitsuyoshi") is old Japanese mathematician. He wrote "Jinkoki". In this book, he wrote many mathematical articles. He also wrote many Japanese scales of decimal numbers.
This picture is "TSUBAKI NO ME-A-TE"(Guess the letter on petal or leaf of camellia) in "Jinkoki". This picture might drawn for memorizing scales.
At the bottom-right corner of this picture, there are 21 letters which are used as scales in Japanese language. (Note: In Japanese table format, letters are listed in vertical rows. Vertical rows are placed from right to left.)
There are five branches from the bottom to the top.
Every branches are labeled the numbers of 2nd powers. From the bottom to the top, 1, 2, 4, 8, 16.
If you thought of the 9th letter in the table.
From the bottom to the top, answer whether the letter is on the petal or the leaf of camellia.
I guessed the number you thought of. Which derived by adding the numbers on branches at which you answered "petal".
This game can be explained by binary expression.
This is a 17-syllable poem in "Touchusya" by Fujiwara-no Suketaka in 12th century.
Original: HA NA WA TO RE, HA WA A DA MO NO TO, O MO U BE SHI.
Translation: "pick up all petals. reject all leafs."