"Each domed space appears individually seeking its own particular light to best express its becoming. Some are complex, manifesting sheer brilliance in the use of geometry and demand a very self conscious light to fulfill their expressions; others need the strong clarity of the structural ribs and require only a dim, indirect light; and there is one which is simply the result of the study of a dome based on the surface friction of brick without mortar, the structural concept of the spiral, and a central light that illuminates its very soul." The Sense of Unity p.108.The dating of these vaults remains a highly vexed question, as it was common practice to place new vaults on older pillars. What is clear is that they are contemporary with those of the north-eastern cloister, indeed there are some which are clearly built by the same hand, and that they were probably put in place as part of the first rebuilding of the mosque, as this part lay outside the original scheme and may have constituted a library or madrasa. There is some contemporary evidence to support the view that when the inhabitants of Isfahan looted the mosque for firewood during the siege by Toghril Begh, what they actually took were wooden shelves and doors such as may have been found in a library, bath or treasury, and which may have been adjacent to the mosque without actually forming part of it.