Billy is able to leap tall newel posts in a single bound ... almost.
Actually he can hop up to the stairwell newel post if he takes his time. However, ever since we put the watchtower next to the newel post, Billy tend more or less leaps up the watch tower and then over to the newel post.
As an extension of this, Billy has picked up the habit of going up stairs via a running start down the hall next to the stairs to mount the watchtower, turning around on the newel post, and leaping almost to the landing on the stairs. All this at full speed, which means our nine inch high cat beats the 64 inch high human up the stairs easily.
With the kitten farm now on the market, our realtor suggested we move the watchtower out of the front hall to avoid clutter, which we did.
The next time Billy tried his normal route up the stairs, he aimed for the newel post directly. But he didn't get the height he needed, so he bounced off the railing, and crashed to the carpeted floor. He picked himself up, then proceeded upstairs anyway, no worse for wear.
I think he may not try the newel post from the floor for a while.