you can't
Go back and get it. Take the gold coin from the fountain, and pay your admission to the museum. In the stack of books to the right is the Library Slip.
go to the secret door
This is the first item on the island. Go to the Mordred Musseum and spend it. Get the library slip and go to the castle library.
Just go in the castle and look for the first door on your right.
Go to the library and click on Mc. It will reveal a secret passageway.
To see the solar system on Astro Knights island, go to the Planetarium. (not part of the game, but an interesting view)
The Library Slip is in the Mordred Museum. Whe you have it, you can click the shelf marked McM in the lower aisle of the castle library. This opens the stairway to the dungeon, where you can get some cheese and throw the switch that opens the back gate of the dungeon cell.
Go to the castle, enter the royal library, click on the McM, and go down the stairs. Collect the moldy cheese and pull the lever. Go back upstairs and there you go.
On astro knights after you got the library slip go to the library in the castle. Look at the library slip,it says nonfiction McM.Go to the lower section of the library and click on the waded piece of paper. Then go down and you go right and walk on the cheese and you have it.
Go back to your spaceship on the top of the castle!!
Merlin cannot enter the castle during the game. You should go to the dungeon the back way, by pushing hard on the dirt wall to the tunnel.
go to astro nights and go to the castle and find your rocket on it. Fly back to mordred