 In 1615 he was commissioned by Mathieu Molé, first president of the "parlement" of Paris, to draw up an inventory of the documents which constituted what at that time was known as the "Trésor des chartes".This work occupied eleven years.His manuscript inventory is preserved in the original and in copy in the Bibliothèque Nationale, and transcriptions are in the national archives in Paris, at the record office in London, and elsewhere.