Clavis commercii: or, The key of commerce : Containing an exact, and most concise method of merchants accompts, after the Italian manner, in one hundred propositions; being the most material cases in proper, factorage, and company-accompts, both domestick and foreign: with an example annexed to each proposition. Also a practical waste-book, journal, and ledger, with directions how to ballance the ledger, and transferr the ballance thereof, as an inventory, into a new ledger. Fitted for the use of schools, the contemplation of gentlemen, and the practice of merchants, or others, who desire to be accomplished with the famous art of book-keeping. By John Hawkins, schoolmaster at St. George's Church in Southwark.