Figure 469 in the Encyclopedia of Needlework by Therese de Dillmont. I have the 1971 edition. The online Project Gutenberg version does not have this pattern.
I think that reversing the leans of the decreases in rows 5 and 11 would make the curved lines clearer.
I noticed later that this is essentially the same as Fleurette which has the decreases leaning as I suggested above..
Shown with a cast-on count of 23 stitches.