"The question for me is whether Ankerberg invented this illustration, or picked it up from others." page 2 of posts (by Leolaia)
Leolaia,
The idea of getting an idea of the length of eternity by an illustration of a bird picking up and moving a grain of sand every thousand years is at least 300 years old. From the puritan minister Thomas Watson (lived 1620=1686):-
The torments of hell abide forever....If all the earth and sea were sand, and every thousandth year a little bird should come, and take away one grain of this sand, it would be a long time ere that vast heap of sand were emptied: yet, if after all that time the damned may come outof hell, there were some hope: but this word EVER breaks the heart.
He wrote a number of books which are still in print, and is perhaps the easiest Puritan to read. Perhaps his most useful book has been "A Body of Divinity". covering the whole of essential Bible doctrine.