I was flying rear seat in a 65hp Aeronca Champ with a fellow 
CFI who had never flown stick or taildragger before.  We had 
practiced stalls and spins, and were coming back towards the 
45 entry at about 1500AGL.  I took the controls to demonstrate 
what a hard forward slip looked like.

  A few seconds later, the prop stopped in midair.  Since there
was no starter, I immediately looked for a spot to land.
There were many fields below, but they were very muddy, so
the chance of damaging the plane was high.  I glanced at a drier
dirt road, but there were wires at the end, and I recalled
that the Airplane Flying Handbook said to use big rectangular
fields for emergencies to give a better chance to correct
altitude mistakes (not land long).  So I decided to land in
the muddy field.

  With this decision, now I had plenty of time and altitude,
so I pitched over a bit, and the extra speed helped the prop 
turn a few times, but it didn't start.  I then pitched hard 
over and dove, and at about 200AGL, the engine screamed to 
life at redline.  We pulled out quite near the ground at 
high speed, and headed back for the 45 entry.