It involves just eight coins, but this tricky brainteaser is anything but easy to solve.

The Water Puzzle was first devised by Henry Ernest Dudeney in the 1920s, but almost 100 years on, it is still leaving people stumped.

The puzzle requires you to convert a H shape of coins to an O shape in just four moves - each of which consists of sliding a coin to a position in which it touches two other coins.

It may require some trial and error to complete, but the puzzle is designed to test your ability to think laterally and mathematically.

Advertisement

http://www.nzherald.co.nz/lifestyle/news/article.cfm?c_id=6&objectid=11754801

The left-hand coin of the two that make up the horizontal line in the H is first moved to the top right of the formation.

Next, the coin to the right of this new position is moved to the space in the middle of the top row.

Then there are two coins left to move, both on the bottom right of the formation.

First, move the coin on the top of the very bottom right coin to the left hand side of it, then move the coin left hanging over the right to the middle, to complete the O.

And for those feeling ambitious, you can try to go back from the H to the O again in six moves.

The puzzle comes from a new book, Can You Solve My Problems? by Alex Bellos, which is a compendium of 125 of the best puzzles from the last 2,000 years.

Mr Bellos told MailOnline: "The level is varied. There are some very simple ones that a primary school child could solve and there are ones that I couldn't even solve."

"The idea was to tell the amazing history of puzzles by selecting the most interesting ones."

Henry Ernest Dudeney, who devised The Water Puzzle, was one of Britain's greatest puzzle innovators.

In a forty-year career writing for newspapers and magazines, he devised more classic recreational mathematics problems than anyone else.

Mr Bellos said: "Puzzles are a wonderful but often neglected part of our cultural heritage.

"Britain especially has a rich history of puzzles, from Alcuin of York in the ninth century to Lewis Carroll in the nineteenth and Henry Ernest Dudeney and Hubert Phillips in the twentieth.

"Puzzles are often refined and updated for each new generation. In the book I have rewritten many classics and given my own twist."