[gumby]

Did you never stare straight at the sun as a kid?

Note that sea captains in the age of the sextant were typically blind in one eye by using the sextant on the one star visible during the day (our sun). But this wasn't from a single viewing, it was from many many viewings, presumably the majority of which were while they were midshipman. They were smart enough to sacrifice one eye, covering the other while looking at the sun.

Nevertheless it's a bad idea, especially with both eyes, and eclipses are more dangerous.

[logfromblammo]

Seems like it would have been trivial to put a filter in front of the upper mirror of a sextant during daylight hours to avoid this. I know that the sextant was an optical device that became commonly used after Newton's Opticks was published, and that Newton temporarily blinded himself while researching it, so there might have been an inkling among the educated that staring directly at the sun was dangerous. But I don't know whether optical filters were known then, or came into use later, as adjuncts to photography. It's definitely too soon for arc welding.