A couple of toys that mesmerized me as a kid were the Wham-O Magic Window and the Space Fidget. These were readily available in the 70s at most toy stores and department stores.
The Magic Window was a clear plastic frame filled with colored sand. A very simple idea that delivered some amazing results. When you tilt or turn over the magic window the sand would shift and flow producing some really beautiful landscapes, seascapes and spacescapes. Here is an old commercial lauding the benefits of owning your very own magic window!
Another similar but less known toy was the Space Fidget. a small circular disc filled with some type of magical liquid that changed and responded to touch and heat. I think it was the same material found inside mood rings. I bought one of these at a dime store once and played with it all the time until it finally broke and dried out. Both the Magic Window and the Space Fidget required no batteries, but a little imagination and endless hours of entertainment to a kid growing up in the 70s.