"The book has been sealed and handed over to the museum authorities to keep it in safe custody," police said.
The police have obtained CCTV footages from the museum to identify the visitor who allegedly wrote derogatory remarks on the visitors' book against Nehru on Sunday.
The remarks were signed by one Pramod Ranjan Dey of Bhubaneswar. Local Congress leaders then lodged an FIR against him in Darghabazar police station.
Police are also tracking the telephone number that was written along with the signature of Dey.