An unpublished short story by Charlotte Brontë featuring flogging and embezzling, as well as a poem stuffed with thees and thous, have been discovered inside a book owned by the novelist’s mother.

Maria Brontë died when her six children – the authors Emily, Charlotte and Anne among them – were very young. Among the few possessions she left behind was a copy of Robert Southey’s The Remains of Henry Kirke White, which was “much-treasured” by the family, according to the Brontë Society. Stuffed with annotations, sketches, and markings by various members of the household, the volume just acquired by the society also contains unpublished manuscripts by the teenage Charlotte, stuck in among the pages.

“We knew the book existed but we didn’t know it had these papers in it,” said spokesperson Rebecca Yorke. “They’ve never been published or come to light before.”

Facebook Twitter Pinterest ‘Hugely important’ ... title page of the book inscribed by Patrick Brontë. Photograph: © Randall House

The family sold the book after the death of Charlotte’s father Patrick in 1861. It travelled from the family home in Haworth to the US, where it eventually ended up in the hands of an American book collector. The circle will be completed in the new year, with the volume due to go on display at the Brontë Parsonage Museum in Haworth. The society received £170,000 for the purchase from the National Heritage Memorial Fund, in addition to contributions from the V&A Purchase Grant Fund and the Friends of the National Libraries.

Collections manager at the museum Ann Dinsdale called the book “one of the most significant Brontë items to come to light in many years”.

She described the finds as “hugely important”. The book “was clearly well-used and of great sentimental value to the Brontë children, who lost their mother while they were very young. In addition, the unpublished writings by Charlotte offer new opportunities for research, which is really exciting.”

Both pieces of work relate to the fantasy world of Angria imagined by Charlotte and her brother Branwell in a series of tiny books. “It played a huge part in their lives,” said Dinsdale. “Everything they read and everyone they met in Haworth fed into their imaginary world.”

The short story features a public flogging, embezzling from the Wesleyan chapel, and a “vicious” caricature of the Reverend John Winterbottom – a religious opponent of the children’s father. Winterbottom is “in the middle of the night dragged from his bed” and then “by the heels from one end of the village to the other”, writes Charlotte in the story.

The poem features Mary Percy, the lovesick wife of the king of Angria Zamorna, and “one of the leading Angria characters”, said Dinsdale. “It’s quite an ambitious poem for a young girl, full of thees and thous,” she added.

“Mary thou dids’t not know that I was nigh / Thou dids’t not know my gaze was fixed on thee,” the poem opens. “I stood apart and watched thee passing by / In all thy calm unconscious majesty.”

The pieces have been dated to 1833, when Charlotte would have been around 17. The story runs to 74 lines, and the poem is 77 lines. Dinsdale predicted that it would be of interest to general readers as well as scholars. “It’s of interest to anyone interested in Charlotte’s life, and because of the tragic story of the Brontës, their lives are particularly appealing to a wide range of people,” she said.

Historian Juliet Barker, author of the biography The Brontës, said that “the book alone is a valuable acquisition because of its rare associations with Mrs Brontë before her marriage to Patrick, but its importance is immeasurably increased by the unpublished manuscripts tipped into it”.

According to the Brontë Society, the Southey title is one of Maria’s “rare surviving possessions”, after a box containing all her property was shipwrecked off the Devon coast shortly before she married Patrick Brontë in 1812. It also features Patrick’s Latin inscription, reading that it was “the book of my dearest wife and it was saved from the waves. So then it will always be preserved.”