I had always read, and believed, that Cameron Of Erracht was devised in 1793 upon the raising of The Cameron Highlanders.

So just now I was surprised to read the following, in a Pipe Band's website:

We are proud to wear the Cameron of Erracht tartan.

This is both an ancient clan tartan and is also truly a pipe band tartan, used by distinguished Highland regiments in Scotland and in Canada today.

It originates with Ewen Cameron, who became the first Cameron of Erracht in the early 16th century.

Now I had understood that there's little evidence as to the design process which took place in 1793, but I'd not read that it was a pre-existing clan tartan, and not read that it can be dated to the early 16th century. Does it appear in an early portrait? Is there an early specimen of the tartan itself?