Probably fifty years ago in Model Railroader magazine there was a regular column written by a guy named Jim Findley called "Letters from Jim".
He wrote a fantasy story about a device called a micro colloidial grinder through which a modeler passed a live steam locomotive model.
It was described as a speck of sand. He had (in the story) a complete replica of a steam locomotive cab in which to run trains.
I wish I could find it, but there was a good passage along the lines of..
"He dropped the Johnson Bar into the corner and opened the throttle. On the layout, a micro speck belched smoke and began to move."
14 year old me really loved that.