I decided to stop talking about it and actually get my butt to Point 3987 today. If you look at the 1953 Mt. Wilson topo map, the point is labeled along the ridge between Castle Canyon and the East Fork of Rubio Canyon. For whatever reason it is not identified on later maps.
From the ramada at Inspiration Point, I headed down the One Man & Mule Road a short ways, to where it's possible to follow some use trails up to Point 4668. I then started down the Castle Spur ridge.
The ridge has some animal trails to follow, and signs of perhaps human work from long ago. But it can be a tough scramble at times, with thorny bushwhacking, steep scree, and route-finding around cliffs.
The clouds didn't make my job any easier. But I progressed steadily and could see my goal poking above the mist.
The views of course would be spectacular on a clear day. Still I enjoyed up-close panoramas of the rock formations for which Castle Canyon was named.
After scratching up my legs pretty good, I reached the Point.
A weather-beaten cairn crowned the small summit. I improved it and looked back up the ridge as the haze lifted, revealing Inspiration Point in the distance.
The sense of fulfillment lingered for quite awhile, as I negotiated a radical gully down to the relative safety of Castle Canyon.
While fooling around in the canyon, I happened upon a water mine tunnel.
Unfortunately, about a million ants have taken up residence near this tunnel, so I did not stay long.