I can't believe how well this works.
Take an egg, put it in the box, make sure when using L or R to switch boxes (you must use L or R) that a Pokemon is in the same place in the box before or after it. Then, while looking at that Pokemon, wait until the cycle between Held Item-Type(s)-Nature is about to change from Type(s) to Nature and then switch boxes with L or R. If you got the timing right you can quickly see the Egg's nature.
Maybe I'm out-of-date and everyone else knew about this already, but I thought it was a pretty cool trick. Credit goes to Tara for bringing it up.
Take an egg, put it in the box, make sure when using L or R to switch boxes (you must use L or R) that a Pokemon is in the same place in the box before or after it. Then, while looking at that Pokemon, wait until the cycle between Held Item-Type(s)-Nature is about to change from Type(s) to Nature and then switch boxes with L or R. If you got the timing right you can quickly see the Egg's nature.
Maybe I'm out-of-date and everyone else knew about this already, but I thought it was a pretty cool trick. Credit goes to Tara for bringing it up.