Intelligent Furniture, American Antique glass sliders "Glider's"

Here is an example of intelligent furniture design for ease of relocation . This Claw foot Oak table is a work of American crafts man with many amazing features one of which is beautiful glass bulls under the footage for ease of relocation.  Circa 1800, glass slider's were made later around 1920's
I remember my first lesson in design when making things consider 2 Principal
1. Mobility

2. Clean ability