On August 12, 1883, astronomer José Bonilla was observing sunspots at the observatory in Zacatecas, Mexico, when he saw dark objects begin crossing the face of the Sun. He counted more than 300 of them over the following hours and days.
Bonilla took several photographs on wet plates at a hundredth of a second and published his report in the French journal L'Astronomie in 1886. The pictures show fuzzy, elongated shapes against the solar disc, and they are often called the earliest photographs of unidentified flying objects.
Explanations have included high-flying geese crossing the field of view, insects, and fragments of a passing comet. The birds explanation is the most widely accepted, but the case is still a favourite in UFO histories.