some have altogether too much ; for example , the first edition of the necrotelicomicon has to be kept between iron plates , the true arte of levitatione has spent the last one hundred and fifty years up in the rafters , and ge fordge 's compenydyum of sex majick is kept in a vat of ice in a room all by itself and there 's a strict rule that it can only be read by wizards who are over eighty and , if possible , dead .