What geometric shape did Leonardo da Vinci propose for a pyramidal parachute canopy?

Leonardo da Vinci proposed a square-based pyramid as the shape of his parachute canopy.

The design appears in the Codex Atlanticus, where Leonardo described a linen canopy supported by a pyramid-like wooden framework. His notes gave the canopy dimensions as 12 braccia on each side and 12 braccia in height. A braccio was a historical Italian unit whose exact length varied by place.

Leonardo’s parachute was not a modern round parachute. The pyramid was intended to create a broad, resisting surface during a descent, while the supporting structure kept the fabric open. The design is often called a precursor to the parachute, but there is no evidence that Leonardo tested it himself.

In 2000, British skydiver Adrian Nichols built and jumped with a replica based on Leonardo’s drawing. The replica worked, although it was too heavy for practical modern skydiving and was released before landing.