Safe money says that cat never sat when he wasn't hungry. That isn't so much teaching as it is grudging compliance. If the cat could figure out a way to take the food from your warm corpse his sitting days would be over.
Well if you don't believe the sitting cat, you certainly won't believe that having learned my lesson about sitting, I trained the next pair to come when I whistled. I did it the same way you'd train a dog, I whistled when I fed them and they associated the sound with something good. It used to amuse the neighbors when I'd whistle and two cats would stop whatever they were doing and come running home.