I've done no work on the history of sunglasses, but since a few of us were discussing it the other day in regards to songs, this passage stood out when looking through Don Quixote (trans. John Ormsby):

PART 1 - CHAPTER VIII
While they were thus talking there appeared on the road two friars
of the order of St. Benedict, mounted on two dromedaries, for not less
tall were the two mules they rode on. They wore travelling
spectacles and carried sunshades; and behind them came a coach
attended by four or five persons on horseback and two muleteers on
foot. In the coach there was, as afterwards appeared, a Biscay lady on
her way to Seville, where her husband was about to take passage for
the Indies with an appointment of high honour.