After the 33-mile marker on Highway 2, turn right onto Forest Route 62. At each fork, take the road to the left. The trailhead is on the right a little before the end of the road. The Mt. Persis review contains more thorough directions.
We left the house at dawn and reached the Persis trail at 7:30 AM. I even convinced my father to come along--he didn't know what he was getting into. After about an hour and a half climb up Persis, we skirted around to the right. Our plan was to avoid the boulder fields spotted with tarns by shortcutting the trail. While it involved some bushwhack, most of the traverse was crawling over boulders. Overall, it cut about a half hour out of the hike.
When we reached the main boulder field that descends form Persis' summit, we unfortunately stayed too high and got stuck in cliffs. One must descend below these cliffs and then aim to the right of the next peaks. After skirting around a high spire, we were confronted with a cliff blocking our path. Two possible trails existed, one on the far left and one on the far right. We took the path on the far right both ways.
After summitting the cliffs, we crossed some more tarns and a beautiful meadow on the backside of Persi-Index. A well-defined path cut through the grass, although it soon disintegrated to the forest. Once in the forest, stay as close to the ridge as possible. I cannot overstress hugging the ridge. The trail, at many occasions, appears to turn down the far side (away from Highway 2). These are mostly attempts to deceive you, as a clear trail usually exists just past some barricade along the ridge.
After about an hour later the trail exits onto the near side of the ridge. It crosses a few slopes of talus until it approaches the small peak in front of Index. Using our best judgment, we headed up and to the right, crossing through the woods. We sighted a few pieces of tape, but all ways seemed about equal. Soon we exited the forest and entered a grassy slope, which we ascended. When we ran into another piece of tape, we skirted through some narrow woods.
Now we stood between the small peak and Index. We had two options: to ascend to the left or work far to the right and cut back. I think that the normal route is to go right, but we headed left. It was steep, but with the help of Green Belays we climbed some slopes, bushwhacked through some brief trees, and entered the summit slope of Index.
We reached the summit at 1:30, but we made considerably better time one the way back. We left at 2:00 PM, and even with two stops at some of the tarns (and a swim), we reached the car at 7:30. The sun was setting on our way home, but we had summitted the behemoth mountain--even it if took all day.