This design is based on a ceiling pattern in the 1889 Robert Graves Co. Wallpaper Catalog.  Ceiling patterns are often great rug patterns as they are non-directional and have solved the “corner problem”.  Often when adapting designs from other sources, how the design turns a 90-degree angle was not figured out as it did not need to be.  With ceiling designs, it has and often the corners are the most elaborate part of the design, as in this case.  This is one of the loveliest ceiling patterns we have come across.