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The cubes, which cost the title $7 each, including production and delivery, landed on desks carrying The Economist's logo and distinctive red colour.

A letter sent with the mailer -- developed by Red Card -- said it is virtually impossible to complete the puzzle without the relevant knowledge.

"In the same way that you need proper knowledge to succeed in business, The Economist can give you this business knowledge," said Tim Pinnegar, regional ad manager at The Economist.

"The Economist team in London loved the idea so much that they have just ordered 200 for use in the UK.

He added: "Media executives and clients are being bombarded with sales messages and promos. We want to stand out from this crowd with a message that is memorable, relevant and brings a smile to the person's face."

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