There sighs, lamentations and loud wailings resounded through the starless air, so that at first it made me weep; strange tongues, horrible language, words of pain, tones of anger, voices loud and hoarse, and with these the sound of hands, made a tumult which is whirling through that air forever dark, and sand eddies in a whirlwind.
Open your mind to what I shall disclose, and hold it fast within you; he who hears, but does not hold what he has heard, learns nothing. Beatrice - Canto V 40-42