Yep. Seen one about 20 years back now.
Was in a small historical village at about 2 a.m. one hot, summer night. Walking along the sidewalk past a very old church (built in 1802), I happened to glance back and saw a lady walking toward the heart of the village. She was all white, semi-transparent, with a long gown, large hat, gloves and an umbrella...just like the pictures you see back in the 1800's of what folks wore. Well, I was kind of startled...after all, it was late at night and really hot!
I turned back to catch up to my friend, who was walking with me. Asked them to turn around and see the lady behind us. They looked. So did I. No lady.
Can't explain it, but I know what I saw that night...