There is a passage in Richard de Bury, of Durham's, medieval treatise on the love o books which Catholic publishers might display in order to put the Catholic public on its metal. He is discussing all the ways in which grimy clerics can injure books, sticking straw to mark the places, and spilling things between the pages, and cutting off the margins to write letters and he goes on from them to crying children, who must never be allowed to admire the pretty capital letters, because they instinctively want to touch whatever they see.

And from the crying children he descends lower still, and says 'moreover, the laity, who look at a book turned upside down just as if it were open in the right way, are utterly unworthy of any communion with books. Let the clerk take care also that the scullion reeking from his stew pots does not touch the lily leaves of books all unwashed, but he who walketh without blemish shall minister to the precious volumes.

I am grateful to him for that 'also', marking a certain transition in his mind; and it is only fair to add that his next sentence reads: 'And again, the cleanliness of decent hands would be o great benefit to books as well as scholars, if it were not that the itch and pimples are characteristic of the clergy.'

He was, in short, an exacting and fussy bishop, whose motto was 'Do not Touch', and his temper was not sweetened by the knowledge that unlettered hands spoke uncharitably about his great collection of books, and though he said mind their vituperation no more than the barking of dogs, he spent pages answering them that library building was a good work, as it assuredly was in the fourteenth century. He was, indeed a generous lender, who knew that books exist to be read, and not least when they are all rare and valuable.

Taken from Woodruff at Random edited by Mary Craig

Fortunately the Library does not take have such a policy but we do require members to handle our books with the greatest care because they are rare and valuable.