This quotation is widely popping up around the internet and even in some "trail quote" books, and is attributed to John Muir. Nonetheless, the purported quote does not show upin any of Muir's published writings, nor in the John Muir Papers at the University of the Pacific. As read, it sounds more like a description "about" Muir's views of solitude, not an actual quote, likely from one of the numerous Muir biographies or commentaries.
You may want to review this page about "John Muir Misquotes" | vault.sierraclub.org
More quotes by John Muir
The clearest way into the Universe is through a forest wilderness.
The world, we are told, was made especially for man — a presumption not supported by all the facts.
No portion of the world is so barren as not to yield a rich and precious harvest of divine truth.
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When, musing on companions gone,
We doubly feel ourselves alone.
I live in that solitude which is painful in youth, but delicious in the years of maturity.
Attribution
Quote text and notes from Wikiquote: John Muir (page history), available under CC BY-SA 4.0. Source quality and labels are our own summary of what Wikiquote records.