One of my aunts - you know I've got some... - gave me a dmc ball size 100, I've nice memories of her using that size for crochetting a collar, many years ago, I think about 40. Everything could be magic with that size of thread!
At page 12 of Priscilla Tatting Book #1 (1909), there is a beautiful edging, picture 30, I felt the urge to try it out with the tiny size 100 thread. I feel myself very vintage now!!