What shape did Leonardo da Vinci specify for his parachute canopy?

Leonardo da Vinci specified a pyramidal parachute canopy in his 1485 Codex Atlanticus sketch.

His design shows a rigid square-based pyramid covered with linen, intended to let a person descend safely from a height. Leonardo estimated that a structure about 7.2 metres high and wide could support a person, although he did not record a practical test of the design.

The sketch is an early attempt to apply air resistance to controlled human descent. It is often described as a parachute even though it differs greatly from modern fabric canopies, which are usually round, cruciform, or ram-air designs.

In 2000, British adventurer Adrian Nichols built and tested a modernized version based on Leonardo’s drawing. It worked, but Nichols used a separate safety parachute because the historical design was heavy and potentially unstable. Leonardo’s pyramid was therefore a serious conceptual design, not a documented successful flight.