Stair dust corners introduced at the end of the 19th century to make sweeping easier. They keep dust from accumulating in the corners : r/Damnthatsinteresting
Amazon.com: Decorative Star Dust Corner for Stair Steps with Bronze Finish : Tools & Home Improvement
Brass Staircase Dust Corners | Van Dyke's Restorers
Winchester Mystery House - These beautiful intricate "dust corners" are installed on the majority of staircases in Sarah's home! Made popular during Victorian times - this small feature made sweeping the stairs