Sentence:  A Peruvian bookkeeper's <WSD>ledger</WSD> was a regular rope curtain with knots running up and down the ropes. He took to knots because he had no system of writing by which to keep his accounts. Each rope represented an account; the bookkeeper had twenty-four rope accounts on one <WSD>ledger</WSD>—the <WSD>ledger</WSD> being a heavy rope from which all the accounts hung. 
Meaning of the word marked with <WSD> tags:  A book for keeping notes, especially one for keeping accounting records; a record book, a register.