Hazrat Inayat Khan, Sufi Mystic and Musician.
From a chapter on the writings of Rumi in his book The Heart of Sufism.
There is no poet in the world who is not a mystic. A poet is a mystic whether consciously or unconsciously, for no one can write poetry without inspiration, and when a poet touches the profound depths of the spirit, struck by some aspect of life, he brings forth a poem as a diver brings forth a pearl.