Bonilla's objects crossing the Sun

On 12 and 13 August 1883 the astronomer José Bonilla, observing the Sun at Zacatecas, counted several hundred small dark objects crossing the solar disc, each in well under a second, and took at least one photograph. He published the observation in L'Astronomie in 1886 without proposing a cause. The usual reading is birds, insects or seeds close to the telescope; a 2011 arXiv paper by Durand Manterola, Ramos Lara and Cordero argued instead for a fragmented comet passing a few hundred to a few thousand kilometres above the Earth. No other observatory reported the objects, which the comet hypothesis has to explain.

Birds, insects or seeds near the telescope (usual reading); a fragmented comet has been proposed

• Durand Manterola et al. 2011, arXiv:1110.2798arxiv.org
• Wikipedia: UFO sightings in Mexicoen.wikipedia.org