Gettan Osho said, "Keichu, the first wheelmaker, made a cart whose wheels had a hundred spokes. Now, suppose you took a cart and removed both the wheels and the axle. What would you have?"
This one took me a while to figure out, but I guess most of them do. Not that common for me to automatically 'get it'. My solution might be different from Mumon's, but I think I get to the same place he did. I focused on the fact that without wheels a cart cannot function and that Keichu's cart had such intricate wheels. A crude but well-made wheel will function - or allow the cart to function - as well as a beautiful one made by a master.
In his verse, Mumon writes:
When the spiritual wheels turns,
Even the master fails to follow them.
They travel in all directions, above and below,
North, south, east, and west.
I think this addresses the idea that I'm speaking of above. They physical wheel doesn't matter, so long as the spiritual wheel turns.
I may not have this one completely after all. As I'm writing here, I feel like there's still a piece I'm missing. I can think it, but I'm having trouble putting it into words. Maybe I need to meditate some more on this one, after all.