Prayer should take up and turn towards the spiritual order all the powers of our mental, emotional and volitional life. Prayers should be the highest exercise of these powers; for here they are directed to the only adequate object of thought, of love, and of desire. It should, as it were, lift us to the top of our condition, and represent the fullest flowering of our consciousness. For here we breathe the air of the supernatural order, and attain according to our measure that communion with Reality for which we were made.

-Evelyn Underhill, The Essentials of Mysticism

Evelyn Underhill (1875 – 1941 AD) was an English poet, novelist, and mystic in the Anglo-Catholic tradition. Her book Mysiticism, published in 1911, is one of the most highly regarded books on the topic.