Bonilla's objects crossing the Sun

On 12 August 1883 the astronomer Bonilla reported hundreds of small objects crossing the Sun and photographed them over two days.

On 12 August 1883, the astronomer Bonilla was preparing a telescope when he saw objects that seemed to partly block the Sun. Wikipedia says he spent the next 48 hours capturing 447 photographs of them. AAAS Science reports that he saw over 400 small objects cross the solar disk, each in under a second, on 12 and 13 August.

Mexico News Daily says Bonilla contacted Mexico City and Puebla by telegraph, which let their observatories look as well. AAAS Science adds that those observatories saw nothing.

The photographs were published in January 1886 in L'Astronomie, a magazine. Its chief editor put the observation down to migrating animals. Gizmodo notes that UFO writers have since called the images the earliest photographs of UFOs, and that a later study proposed a comet that broke apart as the cause.