Critics have encountered considerable difficulty in explaining the setting of Leonardo's ‘Virgin of the Rocks'. Thus L. H. Heydenreich asserts, ‘Das Bild schildert kein Ereignis der biblischen Geschichte'. A background of apocryphal or legendary material has been postulated and denied. Although biblical history offers no explanation for the rocks, a very simple and obvious source appears in conventional biblical exegesis. A convention arose in the twelfth century where by the Sponsa in the Canticum could be taken as the Blessed Virgin as well as the Church, and this attitude persisted in Catholic countries well after the time of Leonardo. Thus Cant. 2: 13-14 was read as an injunction to the Virgin: Surge, arnica tnea, speciosa mea, et vent, columba mea, inforaminibuspetrce, in caverna maceriæ.