There was an interesting thread on Day Plaids, now closed.

Here are some images showing these being worn in the mid 19th century up through today...















Note that there was not a clear line, in the 1860's, between the sort of thing we call a "piper's plaid" today and a simple bit of tartan thrown over the shoulder. In The Highlanders Of Scotland long plaids are wrapped around the body, sometimes loosely, sometimes tightly, sometimes with a brooch, sometimes without.