The wonders of nature are truly astonishing. Mammalogy technicians at the Royal Ontario Museum preserved a blue whale's 440-pound heart that washed up in Newfoundland. 

Reportedly, a heart of a blue whale can weigh up to 1000 lbs, about the size of a dairy cow! The preservation process included extracting the heart, dilating it with formaldehyde to prevent flattening, shipping it to Germany, plastinating it by replacing water with a silicone polymer, and curing it with a gaseous agent. Wow!

Sources: https://www.wired.com/.../how-scientists-preserved-a-440.../
https://www.fisheries.noaa.gov/fea.../big-hearted-blue-whale
Photo: owned by Royal Ontario Museum