Sorry...can't id faded dried out pressed flowers. Do you have a photograph of the living plant?

Possibly Honesty, Lunaria annua.

Well it's Brassicaceae. Was it originally white or mauve? I'm thinking Hesperis matronalis, Dames Rocket. Can be white but usually mauve.

Here is a link that might be useful: {{gwi:313257}}

I second Hesperis matronalis.

I second Lunaria annua. Not really a wild flower, up in NJ anyway, but it seeds around pretty freely. Hesperis doesn't have such large teeth.

WW

Not Hesperis- the leaves are opposite, not Ialternate, and have large teeth. The flowers were that bright white. You know, I have been thinking it was Honesty for a while, but it just seemed weird finding this in a public forest.