The concept of backup important document, started at least few hundred years ago, but we are still careless about it.
How often do you back up your document and source code? Every day? or every month? Most people started to backup everytime they make modification, but later only backup once in a while, till our hard disk (or system) crash, then we will start to backup frequently again.
The biggest China encyclopedia history book--
Si Ku Quan Shu, completed in year 1781, has seven hand written copies, located in different places.
The concept of backup important document, started few hundred years ago, or earlier. Today hard disk storage are so cheap, making copy with photocopy mahcine is so easy, and I still miss the backup procedure sometimes.
《四庫全書》是中國歷史上規模最大的一大套叢書，在清朝時乾隆皇帝，指派紀旳（紀曉嵐）為總編輯，收集了大量民間與官方的重要書籍，編汇而成。始於 1773 年，完成於 1781 年，歷時九年（一說十年）。