Muir is in Yosemite Valley and decides to hike to the top of Yosemite Falls (which is almost 2,500 feet tall). Of course this is before all the improvements and railings and such that you'll find there now. He literally crawls to the edge of one side of the falls to look down and finds that it's not a sheer cliff. There's a slight slope to it so he can't see all the way to the bottom like he hoped. But he also sees just a little ways below there's a 3-inch-wide ledge that he might be able to shimmy down to get a better view. Weighing whether or not the view of a lifetime was worth the danger of free-climbing on to a 3-inch-wide ledge 2,500 feet in the air, he writes this:
"If I was to get down to the brink at all that rough edge, which might offer slight finger holds, was the only way. But the slope beside it looked dangerously smooth and steep, and the swift roaring flood beneath, overhead, and beside me was very nerve-trying. I therefore concluded not to venture farther, but did nevertheless."
He later writes that the view and the thrill were so overwhelming that he couldn't sleep for two nights afterward.
I believe God calls us to similar risks often, but generally we look over the precipice and "conclude not to venture farther". Faith doesn't always make sense or feel comfortable. Muir also added this thought about that experience:
"...I was not distinctly conscious of danger. The tremendous grandeur of the fall...smothered the sense of fear..."
Translation: The reward crushed the risk! When was the last time you took a step of faith in your life and experienced a victory that left you sleepless for two nights?!
Hebrews 11:1 (NLT)
Faith is the confidence that what we hope for will actually happen; it gives us assurance about things we cannot see.