What is a Muse?
A muse (as used by Tim Ferriss in his book) is nothing more than a business that can generate income without consuming time. It’s at least a partially-automated business. I think of it as more like a side business to whatever else it is you do during the day (be it work or relaxation). In other words, opening up a manufacturing plant is probably not a muse. However, starting a website that sells t-shirts for dogs could be considered a muse. For my purposes, most muse ideas will be internet-based, because this is where you can run with an idea at the lowest cost and probably have the highest chance for success (without risking your life savings).
To quote Tim Ferriss in The 4-Hour Workweek,
“Our goal is simple: to create an automated vehicle for generating cash without consuming time. That’s it. I will call this vehicle a “muse”…Muses will provide the time and financial freedom to realize your dreamlines in record time, after which one can (and often does) start additional companies to change the world or sell.”