(CNN) Members of a federal labor union visiting a Georgia Republican's congressional office Monday said they discovered a 19th-century book on display that they considered "racially offensive."

The American Federation of Government Employees is asking Rep. Drew Ferguson for a formal, public apology after its members said they found the book "General Robert Edward Lee; Soldier, Citizen and Christian Patriot," which presents Confederate ideology.

Union members said that the book -- published in 1897 -- was displayed open to a page reading, "The blacks are immeasurably better off here than in Africa, morally, socially, and physically. The painful discipline they are undergoing is necessary for their instruction as a race, and, I hope, will prepare and lead them to better things."

In a statement provided to CNN Wednesday by his spokesman, Ferguson, the Republican chief deputy whip, said he was unaware the book was even in his office and that it has since been removed.

"The office was decorated by staff and the book in question was underneath a box of military challenge coins. I did not even know it was there," Ferguson said. "When my staff learned about it, they removed it and apologized to the individual who was upset by it."

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