Questing in Serpent's Bluff Redoubt; killed the Hagraven, took the scroll from atop the alter, gate behind it would not open. Placed several books on the alter (took a bit of time to get them to stay,) but that didn't activate the gate. Tried some heavy Foreswarn Armor as well (that took about 15 minutes to stick.) Hit it with fire and ice spells. Even jumped on it. Gate would not open. Left dungeon for Skyrim and re-entered. Tried again, still won't open. Any ideas from here, or just give up the quest and move on?

Are you placing them on the visible pressure plate trigger on the stone table? I am not sure if you are trying to use "altar" as a name for the table, or a name for one of the stands that usually have a book or helm on top of them.
EDIT If you are activating the pressure plate, then it is a glitch.
Some of these glitches can be fixed by saving, exiting the game completely, and restarting the game again with the current save.

Ah ha. Ok I recalled passing by that gear looking item on the stone table and wondered what it was when I couldn't pick it up. Dropped a book on it and the gate opened. Thanks!