London, Wellcome Institute MS. 3946. 100 + 101 + 15 +10 + 15 folios. 200x155mm. 19th Century [1886-91.] [Original correspondence between Poisson and Lucien Bernard Eugène Saint Fargeau (47 letters) from 25/2/1877 to 2/2/1888, on the practise of alchemy, and other materials.]