Four sous/spit

From Marcel Mauss's essay "Techniques of the Body," in Techniques, Technology and Civilisation, a catalog item:

Care of the mouth. Coughing and spitting technique. Here is a personal observation. A little girl did not know how to spit and this made every cold she had much worse. I made inquiries. In her father's village and in her father's family in particular, in Berry, people do not know how to spit. I taught her to spit. I gave her four sous per spit. As she was saving up for a bicycle she learnt to spit. She is the first person in her family who knows how to spit.