Yeats's interest in Byzantine art and civilization began in the Nineties and continued through his life. The first issue of “Rosa Alchemica” (1896) refers to the mosaic work at Ravenna (“mosaic not less beautiful than the mosaic in the Baptistery at Ravenna, but of a less severe beauty”), work which Yeats probably saw when in 1907 he travelled in Italy with Lady Gregory. Unfortunately, Yeats has left us no account of his visit to Ravenna. A revision of “The Holy Places,” final section of Discoveries, made for the 1912 edition of The Culling of an Agate, shows that between 1906 and 1912 Yeats's knowledge of Byzantine history had increased. In 1906 he wrote of “an unstable equilibrium of the whole European mind that would not have come had Constantinople wall been built of better stone;” in 1912 this became “had John Palaeologus cherished, despite that high and heady look … a hearty disposition to fight the Turk.” In preparation for the “Dove or Swan” section of A Vision, which Yeats wrote at Capri in February 1925, and left virtually unchanged in the revised Vision of 1937, Yeats read several books about Byzantine art and civilization and studied Byzantine mosaics in Rome and Sicily. He did not return to Ravenna, being fearful of its miasmal air. Once Byzantium had found a place in “the System,” it shortly appeared in the poetry, first in “Sailing to Byzantium,” and “Wisdom” (1926-27); then changed, though not utterly, in “Byzantium” (1930).