  Aims: Although the time of the Maunder minimum (1645--1715) is widely known
as a period of extremely low solar activity, claims are still debated that
solar activity during that period might still have been moderate, even higher
than the current solar cycle #24. We have revisited all the existing pieces of
evidence and datasets, both direct and indirect, to assess the level of solar
activity during the Maunder minimum.
  Methods: We discuss the East Asian naked-eye sunspot observations, the
telescopic solar observations, the fraction of sunspot active days, the
latitudinal extent of sunspot positions, auroral sightings at high latitudes,
cosmogenic radionuclide data as well as solar eclipse observations for that
period. We also consider peculiar features of the Sun (very strong hemispheric
asymmetry of sunspot location, unusual differential rotation and the lack of
the K-corona) that imply a special mode of solar activity during the Maunder
minimum.
  Results: The level of solar activity during the Maunder minimum is reassessed
on the basis of all available data sets.
  Conclusions: We conclude that solar activity was indeed at an exceptionally
low level during the Maunder minimum. Although the exact level is still
unclear, it was definitely below that during the Dalton minimum around 1800 and
significantly below that of the current solar cycle #24. Claims of a
moderate-to-high level of solar activity during the Maunder minimum are
rejected at a high confidence level.
