What stones should be placed on the bedroom window sill to ward off evil spirits?

The window is the communication channel between our home and outdoor. From the perspective of geomantic omen, the window is also a channel for various gas fields to communicate. In order to avoid bad things or suffocation from coming in through the window, we usually put something on the windowsill to ward off evil spirits. Stones from Mount Tai have been invited to fill the corner at home to ward off evil spirits. In recent decades, more and more people like to collect the ornamental stones of Mount Tai, and there has always been a saying that "there is no stone indoors, and there is no stone in the garden".