Artist-medium, he was the subject of an experiment carried out in 1920 by the international metapsychic institute in Lausanne which made the artist realize a painting of 2m by 1,50 m, in a quasi darkness and in front of an audience of artists and scientists, in order to determine if he was under the influence of a spirit. Lesage took up the challenge and this feat was the subject of a study published by Dr. Osty in 1928.
Jean Dubuffet integrated the artist's paintings into his collection in 1948.
A major retrospective of the artist was held in Lausanne in 1989 and a catalog was published for the occasion. He is cited as one of the most important creators.
His work is important since he left at his death more than eight hundred paintings.
The artist's price is between 10,000 and 50,000 euros depending on the format and subject matter.