This exercise is used in the Spanish Riding School but I have seen the simpler version used by Yogi Bresner as a ridability exercise.
Version 1 (Spanish Riding School)
1 Half 8 metre circle left, renvers towards the short side, then into a ¾ circle left.
2 Back into renvers towards the second ¾ circle then ride out in renvers along the inside line.
3. In the third corner ride a ¾ pirouette left.
4.Come out of the pirouette straight across the centre line, a flying chance and turn right.
5. Repeat the exercise on the right rein.
1 Half 10 metre circle left and either straight towards the short side or ride it in shoulder-in.
2 ¾ circle left, ride out straight towards the next corner (or in shoulder-in).
3 ¾ circle left into the third corner, straight across the centre line and turn right.
4 Repeat the exercise on the right rein.
As you can see from this that you can make the exercise as easy or as difficult as you wish.