Because manuscripts are lost, burned, torn apart or thrown away, it is as complex as crucial to know how many of them still exist for any philologist preparing an edition. Thanks to a (semi-)automatic and fully-open source workflow, we have extracted, structured and annotated hundreds of manuscript sale catalogues published in 19th c. Paris. The obtained level of granularity allows us not only to reconcile different sales of a single item sold multiple times, but also to identify if the manuscript is now kept in a library. Using Sévigné as a test case, we were able to calculate that c. 1% of her manuscripts still has to be found because they are circulating on the private market. All the data we produced remain available for similar research on other authors.