Since forms like *your's* and *her's* are basically always incorrect in modern English, one way to answer your question is to look at the frequency of those words in published books.

I'm not sure how representative the corpus for Google's [Ngram Viewer](http://books.google.com/ngrams) is prior to 1800, but if you [search for "your's, her's"](http://books.google.com/ngrams/graph?content=your%27s%2Cher%27s&year_start=1700&year_end=1900&corpus=15&smoothing=3) you'll see the terms peaking in popularity around Jane Austen's lifetime and virtually extinct by 1850.