Here are Two Sayings about When to Cut Your Nails...
Cut them on Monday, you cut them for health;
Cut them on Tuesday, you cut them for wealth;
Cut them on Wednesday, you cut them for news;
Cut them on Thursday, a pair of new shoes;
Cut them on Friday, you cut them for sorrow;
Cut them on Saturday, you 'll see your true-love to-morrow;
Cut them on Sunday, and you will have ill fortune all through the week.
Here's another version from The Home Book of Verse, Vol. 1 (of 4) edited by Burton Egbert Stevenson (1912):
Cut Your Nails on Monday, Cut Them for News
Cut your nails on Monday, cut them for news;
Cut them on Tuesday, a pair of new shoes;
Cut them on Wednesday, cut them for health;
Cut them on Thursday, cut them for wealth;
Cut them on Friday, cut them for woe;
Cut them on Saturday, a journey you'll go;
Cut them on Sunday, you'll cut them for evil,
For all the next week you'll be ruled by the devil.
Thanks and Acknowledgements
The 1st rhyme and illustration can be found in The Big Book of Nursery Rhymes (circa 1920) edited by Walter Jerrold (1865 - 1929) and illustrated by Charles Robinson.