Moses de Leon, The Book of the Pomegranate, pp. 227-228

Jewish Mysticism
This is called a secret since its matter is hidden, the concealed secret of the Creator, and understand. In its secret is the moon that stands and is hidden… Thus, it is called a concealed secret and it is hidden with her, and in its secret she stands and is swept away. Indeed, the secret of this matter is so that it will bind within itself the secret of the crown (‘ateret).

Translated by Elliot Wolfson in Through a Speculum that Shines- Vision and Imagination in Medieval Jewish Mysticism, Princeton- Princeton University Press, 1994.