Many of the great observers of history counted the number of Pleiads
visible to the naked eye. Some of these observers had exceptional
eyesight, and of course observed without the curse of light pollution
that we suffer from so badly today. The most impressive historical
observers of the Pleiades are as follows:


Maestlin (1550-1631; Kepler's tutor) claimed to see 14 and mapped 11
before the invention of the telescope.

Carrington (1826-1875) & Denning (1848-1931) counted 14.

Miss Airy (daughter of G B Airy) counted 12.

William Dawes (1799-1868) counted 13.

One record of the modern era is by O'Meara who claimed to discern 17
Pleiads by naked eye in 1978 at Cambridge, MA, USA.

I would say that any really experienced observer with fairly good
eyesight and excellent skies, should be able to see at least a dozen
Pleiads naked eye. When I enjoyed very good skies back in the 60's and
70's, I saw 14 stars repeatedly and suspected several more. Likewise,
on the best nights long years ago, I could often detect the enveloping
nebulosity surround the cluster without optical aid.

It's also very true that light pollution has taken so much away from
the extreme visual limits commonplace a century and more ago that few
observers today realize just how much "should" be visible without
optical aid.

JBortle