Previously unseen drawings of Winnie-the-Pooh that show the honey-loving bear before he was introduced to generations of readers in the 1926 book have come to light.

Two preliminary pencil sketches by E H Shepard have been shared for the first time by his family to mark the centenary of one of the most loved books in children’s literature.

Having been abandoned at the very earliest stage of the book’s creation, the drawings offer a rare glimpse into Shepard’s working process and imagination as he brought AA Milne’s character to life. They depict passages that are familiar to readers but were not accompanied by illustrations in the original published book.

A pencil drawing, captioned: “Climbing very cautiously up the stream”, shows Pooh and his adventure-loving friends Christopher Robin, Piglet and Owl. It was intended for Chapter VIII, in which Christopher Robin leads an “expotition” to the north pole.

In that passage, Milne wrote: “‘We are all going on an Expedition,’ said Christopher Robin, as he got up and brushed himself. ‘Thank you, Pooh.’

“‘Going on an Expotition?’ said Pooh eagerly. ‘I don’t think I’ve ever been on one of those. Where are we going to on this Expotition?’

“‘Expedition, silly old Bear. It’s got an ‘x’ in it.’

“‘Oh!’ said Pooh. ‘I know.’ But he didn’t really.”

Another sketch that never made the final book is a delicate study for Chapter III, in which Pooh and Piglet go hunting and nearly catch a Woozle.

The drawings will be shown at Peter Harrington Rare Books in Dover Street, central London, as part of an exhibition that opens on 17 April.

Philip W Errington, a senior specialist at Peter Harrington, described the drawings as “very special”. He said: “[In] these preliminary sketches, Shepard’s putting these first thoughts on paper and there’s an absolute, vibrant creativity going on there.

“The skill that he’s got in rendering movement is really quite exceptional. The pencil marks across that page are really beautifully done. You’ve got the rapid creativity plus Shepard’s hallmark movement. These pieces really do leap off the page.”

He added: “It is extraordinarily rare to encounter preliminary drawings of Winnie-the-Pooh that capture what might be called the first moment of inspiration – the instant where Shepard is thinking through movement, character and narrative in pencil alone.”

He said of “Climbing very cautiously up the stream”: “You can see Christopher Robin at the front. [Pooh] is really very distinct and Piglet is beautifully done, but he’s got a little arrow at the bottom where he’s put ‘closer’. Perhaps he was having a bit of a problem with how those characters appear on the page. You’ve also got Kanga and Eeyore.”

Errington was an adviser to a 2017 Shepard exhibition staged by the Victoria and Albert Museum, to which the artist had bequeathed most of his preliminary drawings in 1969. “There are two types of drawing – the preliminary drawings, usually done in pencil, where he starts to create and play with the image and work out what is going to happen, and the finished drawings,” he said.