Image copyright Randall House Image caption The prose fragment "has references to lots of people who genuinely lived in Haworth at the time" including sending up the local methodists

Unpublished manuscripts by Charlotte Bronte have been discovered inside a rare book belonging to her mother.

A poem and short story written by the author as a teenager were found between the pages of a biography of poet Henry Kirke White, owned by Maria Bronte.

Bronte specialist Dr Juliet Barker called the find "extraordinary".

The book and manuscripts are in the process of being acquired by the Bronte Society for £200,000. The Bronte Museum hopes to put them on show next year.

Dr Barker, who wrote a seminal history of the Bronte Family, told the BBC she was "astonished" when she heard about the newly discovery material.

"It's so unusual to get unpublished manuscripts in this day and age. To find an unpublished one like this - that we had no knowledge of its existence - is extraordinary."

Image copyright Randall House Image caption Poet Henry Kirke White had attended Cambridge with Patrick Bronte, and the volume includes notes scribbled by Patrick Bronte.

Maria Bronte's copy of Robert Southey's The Remains of Henry Kirke White was among a few treasured possessions salvaged after a boat carrying her belongings - prior to her marriage to Patrick Bronte - was shipwrecked off the Devonshire coast in 1812. To this day, it is stained with salt-water.

Inside it bears a Latin inscription, in her husband's writing, which states it was "the book of my dearest wife and it was saved from the waves. So then it will always be preserved".

The book itself contains annotations and sketches by members of the Bronte family, as well as the poem, story extract and a letter by Arthur Bell Nicholls, Charlotte's husband, written shortly after the author's death in 1855.

Dr Barker believes there is "no question" of the manuscripts' authenticity, citing Charlotte Bronte's distinctive handwriting - which varied according to the type of material she was writing - as well as the contemporary detail and Charlotte's use of her "favourite" male pseudonym, Lord Charles Wellesley.

Set in 1833, the short story fragment - described by Dr Barker as a "satirical take on life in Haworth" - is 74 lines long and written in the character of "the debonair, man-about-town" Lord Charles.

Image copyright Randall House Image caption The incomplete poem was written in Charlotte Bronte's "tiny" handwriting intended both to save paper and hide the contents from her father's failing eyesight.

Highlighting the significance of the manuscript, Dr Barker stressed the "insight [it gives us] into Charlotte's character".

"Charlotte much preferred to write as a man," she explained. "It allowed her to go, as a writer, to places she couldn't go as a woman."

The incomplete "dramatic" poem is 77 lines and revolves around the fantasy world of Angria, which Charlotte dreamt up with her brother, Branwell, in childhood.

Dr Barker described it as "typical" of the poems she wrote. The first quatrain reads:

Mary thou dids't not know that I was nigh

Thou dids't not know my gaze was fixed on thee

I stood apart and watched thee gliding by

In all thy calm unconscious majesty

Image copyright PA Image caption The Bronte sisters - Charlotte, Anne and Emily - were born between 1816 and 1820

With the help of funding from the National Heritage Memorial Fund, the V&A Purchase Grant Fund and the Friends of the National Libraries, the Bronte Society is currently in negotiations to acquire both Maria Bronte's book and the Charlotte Bronte manuscripts.

The book was originally sold following the death of Patrick Bronte in 1861 and has been held by the same family in the US for nearly 100 years.

It is believed to have been offered for sale just once previously, in 1918 - but it was either withdrawn ahead of sale or no buyers were found.

The forthcoming bicentenary of Charlotte Bronte's birth next year, which will be marked around the world - including an exhibition about the Brontes in New York - is thought to have precipitated the current sale.