At the end of next month, Comet ISON is expected to be at its brightest, when it is nearest to the Sun. Still, no one knows exactly what it will look like. And so, to provide a hint, NASA dug up the image above, which is Comet Kirch, the Great Comet of 1680 that is pictured above a crowd of Rotterdam in the Netherlands. Some people in the crowd are holding cross-staffs, a primitive angle measuring device.
This image is a painting by Lieve Versheier, and it represents the moment when Comet Kirch was also nearest to the Sun.