Here the left refer to a well-known poem by the famous Chinese Buddhist monk, Chih-i (智者), and originally included in the Treatise on the Great Cessation and Contemplation (Mo-ho chih-kuan 摩訶止觀), although the poets would have know it from its inclusion in the Collection of Japanese and Chinese Poems to Sing (Wa-Kan Rōei-shū 和漢朗詠集):

When the moon is hid ‘hind rangéd mountains,
I lift a fan to take its place,
When the wind blows in the Void
The trees do move, and so I teach!

In the above poem, the moon and wind represent inexpressible Buddhist truth, which can only be taught by representation, or by viewing its effects.