In the spring, when snow melt is high, the Horsetail Waterfall can be incredible. This trail is accessed from the Pyramid Creek Trailhead. You can use the Pyramid Creek Loop Trail to access this trail and to see some additional scenery along the way. Once you've made it onto this trail, you'll continue up to the wilderness boundary.
You'll scramble a bit over granite outcrops, and you might feel like you've lost your way at times, but essentially, you'll be headed straight up towards the falls, with the creek on your right. When you get to the falls, it's possible to continue beyond the end of the marked trail, but don't attempt this unless you're a skilled backcountry hiker. It's slippery and potentially quite dangerous towards the top of the falls.