The original goniostat as outlined by Charles Holtzapffel in his 1850 book, Turning and Mechanical Manipulation, Vol. 3 - Abrasive and Other Processes not Accomplished with Cutting Tools. This was designed to work with a flat stone, though now these are used with flat spinning disks, and a newer variation of it is still available.
Lukin designed the Goniostat below and published it in 1894.
A more modern one is shown to the right, and drawings by Mike Fallows are below.
One I designed and made for use on a Tormek sharpener is below that.