May den Engelsen’s first book illustration commission was for the Paris publisher René Kieffer’s La Centaine press in 1925. It was to illustrate Les amies by Paul Verlaine, a cycle of six lesbian-themed sonnets first published in 1867 under the pseudonym Pablo de Herlagnez. Les amies  was part of Verlaine’s notorious Oeuvres libres, which were officially banned by the French government until 1949. However, they circulated widely underground, and it was almost the duty of any erotic illustrator to provide a graphic accompaniment to Verlaine’s verses

May’s constant partner and co-conspirator Frans also contributed seven illustrations, and they worked together on the project, producing the prints on the hand-press aboard the Marie-Jeanne.

May produced seven engravings for the book, one for each of the sonnets, ‘Sur le balcon’, ‘Pensionnaires’, ‘Per amica silentia’, ‘Printemps’, ‘Été’ and ‘Sappho’, plus a frontispiece and introductory plate. A total of 111 copies were printed, of which fifteen were specially bound in luxury bindings with an extra set of plates.