Simplify the following text for a Grade 15 native English-speaking person.
Original: According to Galen , Ptolemy III requested permission from the Athenians to borrow the original scripts of Aeschylus , Sophocles and Euripides , for which the Athenians demanded the enormous amount of fifteen talents ( 450 kg of a precious metal ) as guarantee .
Simplified: According to Galen , Ptolemy III requested permission from the Athenians to borrow the original scripts of Aeschylus , Sophocles and Euripides , for which the Athenians demanded the enormous amount of fifteen talents as guarantee .