The term 'ancient' normally describes a change in colour that can be applied to any tartan. In the case of MacMillan the 'ancient' form involves a more radical change, justifying the traditional use of the adjective in the name of the tartan. James Logan, co-author of 'The Clans of the Scottish Highlands' (1847), states that this version is identical with Buchanan. The thread count was deduced by J. Cant from the illustration by R.R. MacIan in the same work.