The roots of classical philology lie in the Renaissance, as humanist intellectuals attempted to return to the Latin of the classical period, especially of Cicero, and as scholars attempted to produce more accurate editions of ancient texts. Some of the principles of philology still used today were developed during this period, for instance, the observation that if a manuscript could be shown to be a copy of an earlier extant manuscript, then it provides no further evidence of the original text, was made as early as 1489 by Angelo Poliziano. Other philological tools took longer to be developed: the first statement, for instance, of the principle that a more difficult reading should be preferred over a simpler one, was in 1697 by Jean Le Clerc.