Roy B. Kester, Accounting theory and practice… (1922)
“ Proving the Customers Ledger.—The use of a controlling account in the general ledger, however, does not eliminate the necessity of proving the accuracy of the customers ledger. It merely makes it possible to take a trial balance without bringing the numerous customers’ accounts into it. It is just as much a part of the proof of the work to make a list of customers’ accounts balances and check it against the balance of the Accounts Receivable general ledger account, as it is to prove the general ledger by means of a trial balance. ”
