The simple butterfly, folding table leaf has been around since at least the 1880’s. I have a client who had a custom table with 2 butterfly leaves made in Denmark some decades ago. I built for them, off their table idea an oval table with 3 butterfly leaves. The trick with an oval table is the lack of real-estate space inside a solid table base; not veneered. I had to machine slots on the end rail for the table halves to be supported with maple runners for the table top to extend an extra 20″ on each side. Using just the center leaf allows 2 extra people, one on each end. The beauty of this addition is the table extends to a circular shaped table for conversational benefit.  With the center leaf and one of the mini leaves added it adds the eleventh person at either end