Compared with the 18th century therearen’t many stays still around from the 17th century. There isn’t much written about them either- I suspect there are a buried treasured hidden in museum collections that no one has ever bothered about. Here I have collected information of the extant stays I know about. To not make the post too long, I’ve saved the boned bodices of that period for a later post.
The oldest stays we have are German and dated to 1598. It was part of the burial clothes for Pfaltzgrafin Dorothea Sabine von Neuberg and is described by Janet Arnold in i Patterns of Fashion 1560-1620 (You can also find the pattern in Corsets and Crinolines by Norah Waugh. It’s made out of two layers of linen and one of silk, boned with whalebone. There is a pocket in the front for a busk, laced in the back and, as you can see from the picture, there is no boning over the chest.
(Picture source: http://www.elizabethancostume.net/corsets/history.html)