E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A mundane period of years, four of which have already passed, making up an aggregate of four million solar years. In the first period men were innocent and free from disease, in the second their life was shortened by one quarter. In the first period devotion was mans object, in the second spiritual knowledge, in the third sacrifice. Compare the Hindu legend with the account given in Genesis.