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Large sunspots can be observed with the unaided eye under suitableatmospheric seeing conditions. Such observations are of particular valuebecause the frequency of their appearance provides an approximate indication ofthe prevailing level of solar activity. Unaided-eye sunspot (UES) observationscan be traced back well before the start of telescopic observations of the Sun,especially in the East Asian historical records. It is therefore important tocompare more modern, UES observations with the results of telescopic sunspotobservations, to gain a better understanding of the nature of the UES records.A previous comparison of Chinese UES records and Greenwich photo-heliographicresults between 1874 and 1918 indicated that a few of the UES were apparentlynot supported by direct photographic evidence of at least one sunspot with alarge area. This article reveals that one of the Chinese unaided-eyeobservations had possibly captured the transit of Venus on 9 December 1874. TheChinese sunspot records on this date are compared with Western sunspotobservations on the same day. It is concluded that sunspots on the solar diskwere quite small and the transit of Venus was probably misinterpreted as asunspot by the Chinese local scholars. This case indicates that sunspots orcomparable "obscuring" objects with an area as large as 1000 millionths of thesolar disk could easily have been seen with the unaided eye under suitableseeing conditions. It also confirms the visibility of sunspots near the solarlimb with the unaided eye. This study provides an explanation of the apparentdiscrepancy between the Chinese UES observation on 9 December 1874 and theWestern sunspot observations using telescopes, as well as a basis for furtherdiscussion on the negative pairs in 1900 and 1911, apparently withoutsufficiently large area.

A Transit of Venus Possibly Misinterpreted as an Unaided-Eye Sunspot Observation in China on 9 December 1874