Seamus Heaney's famous line to "walk on air against your better judgement" has been inscribed as an epitaph on his gravestone.

The quote, from Heaney's 1995 Nobel Prize for Literature acceptance speech, was placed over the poet's grave in Bellaghy, Co Derry earlier this week.

The line was included in a poem called The Gravel Walks.

Heaney, who died almost two years ago aged 74, was Ireland's best known contemporary writer.

He is buried in Bellaghy, his birthplace and the inspiration for much of his early work.

Historian Eugene Kielt runs tours of Heaney country. He said: "It is a beautiful line, very inspirational. It is about going for it. We are naturally cautious and sometimes someone should throw caution to the wind.

"It is about keeping your feet on the ground but looking up as well. It is about risk taking and not being inhibited, losing your inhibitions."

The line was first used in a poem published in the US. In 1996 it formed part of the collection The Spirit Level.

In a 2008 interview Heaney was asked why he chose it.

He said: "A person from Northern Ireland is naturally cautious. You grew up vigilant because it's a divided society. My poetry on the whole was earth hugging, but then I began to look up rather than keep down. I think it had to do with a sense that the marvellous was as permissible as the matter-of-fact in poetry."

Heaney has said The Gravel Walks was about heavy work as well as the "paradoxical sense of lightness" when lifting heavy things. It also reflects a popular traditional Irish reel of the same name.

"I like the in-betweenness of up and down, of being on the earth and of the heavens. I think that's where poetry should dwell, between the dream world and the given world, because you don't just want photography, and you don't want fantasy either."

Professor Fran Brearton, director of the Seamus Heaney Centre at Queen's University Belfast, said it was a line that referenced his early work about digging in his native home.

She explained: "It is about being able to see beyond your moment, he says it is a reminder to himself about what poetry can do.

"It is about not being dogmatic, grounded, intransigent, nor completely remote from everyday life ... it is about trying to find a balance between things."

She said that could be interpreted politically but was also about the balance between his past and childhood and how that is married with adulthood.

The line is taken from the final stanza of The Gravel Walks, the full verse of which reads:

"So walk on air against your better judgement

Establishing yourself somewhere in between

Those solid batches mixed with grey cement

And a tune called The Gravel Walks that conjures green."