Well I do not believe women during the 1900 or earlier removed their ribs it was no need for. They all started to wear a corset at a young age when the ribs was soft and could easily be shaped.
Compare it to women during the 50's who used girdles (and corsets) they also had a nice hourglass shape something you no longer sees in modern women who never ever wear anything tightfitting around the waist and torso and thinks their waist is at hiplevel.
It is possible even at a older age (stiffer ribs) to shape the ribs just look at Cathie Jung she has X-rays to prov no ribs are removed http://waist-trainer.org/black-cashmere-underbust-corset-review. I have also shaped my ribs at an older age and I think anyone who is really interested in corsets and tightlacing feels it is wrong and a fake thing to do to remove the ribs insted of do 23/7 corsettraining. For me tightlacing is a lifestyle I do for myself to look and feel good.
This article has some interesting pictures how photos was manipulated to show a smaller waist and they also write about the myth ribs was removed. Like jealousy being a part of the myth and this I can believe. I for example has been asked a couple of times if I have some eatingdisorder because of how I look and no I do not. I eat small meal several times a day (around 6 times) to not loose weight but I also stays laced 23/7 for real.
This is the X-ray photos of Cathie Jung with her ribs still intact but shaped. It is totally possible to shape the ribs if you do it slowly over many years. I have read on several places some people who thinks her ribs are removed. But the stupid thing is it does exist people today who do remove their ribs.