Christie's said it was suspending the Paris auction of one of just a handful of examples of the world's first calculating machine, developed by French mathematician and inventor Blaise Pascal in 1642.
The auction of "La Pascaline" had been scheduled for this afternoon, but late yesterday a Paris court suspended authorisation for export - meaning buyers would not be able to take it abroad.
This example is one of only nine still existing and the only one believed to be in private hands - others are held in museums.
Christie's had dubbed the box, decorated with ebony, as "the most important scientific instrument ever offered at auction" and it had been expected to fetch €2-3 million.
The auction house had described the machine as "nothing less than the first attempt in history to substitute the work of a machine for that of the human mind".
It said it had halted the sale at the instructions of the piece's owner, after the Paris administrative court suspended an export authorisation in a provisional ruling.
The sale, part of an auction of the library of late collector Leon Parce, would be suspended pending the final decision by the court, Christie's said.
"Pending the final judgment, given the provisional nature of this decision and in accordance with the instructions of its client, Christie's is suspending the sale of La Pascaline," it said.
Scientists and researchers had urgently appealed to the administrative court to block the potential export of the machine.
They want the instrument to be classified as a "national treasure".
The culture ministry said an export certificate had been issued in May following standard procedures.
Two experts - one from the National Centre of Arts and Crafts (CNAM) and the other from the Louvre Museum - approved the decision, the ministry said.
Blaise Pascal was only 19 when he developed the machine to help his father, who was in charge of a court that was tasked with restoring order to tax revenue collections in northern France, Christie's said.
"To simplify these tasks, Blaise Pascal designed calculating machines that, for the first time in history, allowed for the mechanisation of mental calculation," it said.
The final court decision could take several months.
