That pyramid is called Dale's Cone of Experience, created by Edgar Dale in 1946.
The percentages were not part of his original pyramid, they are just made up. And there is no research verifying the 'order' of the parts of the pyramid, either.
From Wikipedia: "Dale's "Cone of Experience," which he intended to provide an intuitive model of the concreteness of various kinds of audio-visual media, has been widely misrepresented. Often referred to as the "Cone of Learning," it purports to inform viewers of how much people remember based on how they encounter information. However, Dale included no numbers and did not base his cone on scientific research, and he also warned readers not to take the cone too seriously."
Although the learning pyramid may be accurate, the research on which the figures is based has either gone missing or never existed.
The given source is the National Training Laboratories in Bethel, Maine. However, they happily admit that they're unsure how it came to have figures.
"Yes, we believe it to be accurate - but no, we no any longer have - nor can we find - the original research that supports the numbers. We get many inquiries every month about this - and many, many people have searched for the original research and have come up empty handed.”
The mantra when I was an intern learning procedures (drawing an arterial blood gas, placing a subclavian line, etc) was: watch one, do one, teach one. The "one" part is a little scary, looking back, but the concept is valid.