It is generally well known that the “Chair of Unity Octave” was an Anglican, or more particularly Anglo-Papalist creation, by the Episcopalian Priest The Rev’d Lewis Thomas Wattson (1863-1940), who earnestly sought the re-union of Christendom. Wattson founded an order based on Franciscan spirituality: the Society of the Atonement. This was founded in 1898, and Wattson took the name Paul James Frances.
The first Octave of prayer for unity took place in 1908, and its first fruit was the corporate submission of the Society of the Atonement in 1909: as a Catholic order: the Friars of the Atonement: they were highly successful in vocations and were able to propagate the Octave, it being extended to the whole Catholic church by Benedict XV.
You can read more About the remarkable Fr Paul of Graymoor, whose cause for canonisation is currently open, here. If you are really interested, there is also a silent video of him clothing novices for the Order of the Atonement here.