Wings are seldom sufficient to suggest lightness in the air, because they can scarcely be designed of the size and strength which we judge to be proportionate to the presumed weight of the body, without making the form appear abnormal, though there are instances in which partial success has been achieved by using comparatively small figures and giving them unusually large wings.[a] The use of more than a single pair of wings is hardly permissible because of the apparent anomaly. Actually one pair is not less incomprehensible from an anatomical point of view than several pairs, but custom has driven from our minds any suggestion of incongruity in respect of the representation of the common type of Angel. Naturally when skilfully arranged, the more wings, the stronger the illusion of flight, and if a habit of giving four wings to an Angel were engendered, we should perhaps see nothing strange in them. Even six wings have been given to Angels without making them appear ungraceful.[b] [a] J. H. Witt's Bless the Lord. [b] Picart's The Burning Coal. When there is no assistance, as clouds or flowing drapery, lent to Angels to promote the illusion of suspension, it is necessary to give them an attitude which is nearly horizontal. Properly managed, a pair of comparatively small wings may in this way appear to support a heavy form.[a] Luini actually adds the weight of the body of St. Catherine to three Angels, flying horizontally, who carry her to the tomb[b]; an invention, strangely enough, followed by Kulmbach in Germany at about the same time.[c] In both cases the illusion is excellent. Some of the early Flemish and German masters, including Van Eyck[d] and Holbein,[e] employed Angels in scenes with the Virgin to hold suspended behind her seat, large falls of brocaded material, and it is curious to note that the Angels themselves seem to be supported by the drapery. In order to assist the suggestion of lightness, Perugino sometimes arched the lower limbs of the Angels, adding a narrow tape scroll[f]; an addition improved upon by Raphael who substituted for the scroll a loosened girdle flying out from the waist.[g] [a] Rembrandt's The Angel quitting Tobias, Louvre. [b] The Brera, Milan. [c] St. Mary's, Krakan. [d] Virgin and Child at the Fountain, Antwerp. [e] Virgin and Child, Augsburg. [f] The Ascension, Borgo San Sepolcro, Perugia. [g] Creation of Woman, Castello Gallery; Prophets and Sybils, Perugia, and others.