“You may return here once you have fully come to understand that you are always here.”

This quotation was first used in print (and misattributed to Leonardo da Vinci) in a science fiction story published in 1975, The Storms of Windhaven. One of the authors, Lisa Tuttle, remembers that the quote was suggested by science fiction writer Ben Bova, who says he believes he got the quote from a TV documentary narrated by Fredric March, presumably I, Leonardo da Vinci, written by John H. Secondari for the series Saga of Western Man, which aired on 23 February 1965. Bova incorrectly assumed that he was quoting da Vinci. The probable author is John Hermes Secondari (1919-1975), American author and television producer.
Misattributed
Variant: For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return.

Source: Message in a Bottle

Source: Ghost Town

Quotes from Judge Judy cases, Dress, stand, speak properly
Source: http://www.youtube.com/watch?v=kt3L8c0Dv_M&feature=related

Speech rejecting the demands that he lead his people onto a reservation. (1876)

Part V, Ch. 3
O Pioneers! (1913)

The Lost Son," ll. 168-172
The Lost Son and Other Poems (1948)