Somewhat ironically given this question, the modern concept of Scottish clan tartans is exactly that: modern. The idea of each clan having its own distinctive pattern was made up in 1842 by a book called the Vestiarium Scoticum, a forgery purporting to be reproduction of an ancient manuscript that was produced as part of the romantic revival. Prior to this, while Highlanders did wear tartan, what pattern they wore largely depended on taste and what materials were available: David Morier's famous painting of the Battle of Culloden, painted in 1746 just a year after the rebellion ended, shows eight Highlanders wearing between them twenty different patterns of tartan.