The horse shit is all bullshit; In the thirties and forties, furniture was stuffed with horse hair or cotton. Car seats were mostly steel springs and covered in burlap and then covered with cotton. There was a couple of large sofa factories in Tijuana and and a lot of the upholstery guys had worked there as kids, so they had a lot of expreriance sewing and cutting patterns and that in turn created a large work pool for doing car upholstery. In the late 50's foam was invented so horse hair became obsolete and a lot of the surplus from the furniture factories were sold to the upholstery shops. So where did the "horse shit " story come from ? Well either some body ripped a fart and crapped there horse hair stuffed seat or the more logical explation is this; In the late 60's and 70's , one of the curio shops had the novel idea of rewrapping the cheap 10 cents a pack Mexican cigarettes and calling them horse shit cigarettes as a novelty and joke. And pretty much if you ever smoked one , that's what they tasted like. They had no filters and since they came from Mexico city, they were always stale and dry.