Britannia Depicta, a series of early 18th Century road maps is in the collection
An action group says it is "aghast" at plans to sell some of Wales' oldest and rarest books.
Cardiff Council could eventually sell up to 18,000 items dating from the 15th Century at auction to raise money for improvements in library services.
The collection at the central library includes early atlases along with a second edition of Shakespeare.
An initial 139 items are being assessed but the group, which includes academics, wants an end to the process.
The council says all proceeds from the sale will be re-invested back into the whole Cardiff library service.
Cardiff Council said auctioneers Bonhams have identified an initial list of 139 titles to consider.
"As you will appreciate we have nearly 18,000 items to review and this will be undertaken in a staged process over several years, "said a spokesman.
He said the council intended to keep the 13th Century Llyfr Aneirin (The Book of Aneirin), the manuscript collection (including the Captain Scott manuscripts and Bute papers).
Also being retained are early printed Welsh books and bibles, including a Bishop Morgan bible.
"The items for review include some incunabula and the private press, special bindings, limited editions and rare book collections," said the spokesman.
But campaigners insist selling the collections will "be a step backwards" for the city.
Peter Keelan, head of special collections and archives at Cardiff University Library, said he understood the first batch of books date back to the 1500s and were probably the most valuable of the books being sold.
He estimated that some individual volumes could fetch in the region of £30,000 to £40,000.
"We are in discussions with the council about whether we could buy some of the books but the prices they could fetch at auction would be beyond what we could afford," he said.
"Nothing has come of the discussions yet but we have the capabilities of looking after books of that age - we have books going back to 1508 - and so if the council says they cannot afford to keep them and care for them, we could. It would also mean people from all over Cardiff could see them."
The city's collection includes a Tyndale's bible, one of the earliest translated and published in the 16th Century; key English and European texts from the Protestant Reformation; a substantial collection of scarce political tracts from the Civil War and rare books on natural history and geography.
Mr Keelan said: "There is nothing else here in Wales as the library in Aberystwyth concentrates more on Welsh texts. Students would have to go to London for their research. If these books disappear from Cardiff, research will grind to a halt."
A new action group, Cardiff Heritage Friends, which includes local residents, historians, other academics, solicitors, and librarians, is calling for the council to stop the sale "of some of Wales' greatest treasures".
Group member Dr Wyn James, who is also secretary of Cardiff Welsh Bibliographical Society, said: "A lot of people are aghast about this. For Cardiff, having these books is the difference between Cardiff being a local and Welsh interest library to being a library in the international league.
"In the past the council has not invested in these books and did not include them on the electronic catalogue, which means that the majority of people did not know they were there.
"But rather than ensuring that these valuable collections be catalogued, and exploiting these assets in a way that would substantially enhance Cardiff's prestige as a city of culture and learning, the council has decided to sell them."
A council report in 2007 said it would cost the authority £2-3m to look after the collections.
A spokesman for Cardiff council said the sale would allow the authority to "provide high quality 21st Century services for all Cardiff residents".
"Improvements will include technological advances that will benefit all library users across the city," he said.