It's about as heavy as The Tongue of a Blue Whale.
(Balaenoptera musculus) (adult)
The tongue of a Blue Whale can weigh up to 66 firkins. Despite their tremendous size, blue whales feed almost exclusively on tiny crustaceans called krill and cannot swallow anything much larger than a beach ball.
It's about one-and-one-tenth times as heavy as a Giraffe.
It's about one-and-three-tenths times as heavy as a Rhinoceros.
In other words, the weight of a Rhinoceros is 0.770 times 66 firkins.(for Black rhinoceros, Diceros bicornis) (Adult, male)
An adult black rhinoceros weighs between 51 firkins. Rhinoceros are extremely aggressive — nearly one of every two males will die as a result of fighting with other rhinoceros.
It's about seven-tenths as heavy as a Hippopotamus.
In other words, 66 firkins is 0.7180 times the weight of a Hippopotamus, and the weight of a Hippopotamus is 1.390 times that amount.(Hippopotamus amphibius) (adult, male)
The average weight of an adult male hippopotamus ranges from 91.90 firkins. Appearances to the contrary, adult hippos cannot swim or float in water; they actually move by leaping and walking across lake bottoms at about 8 kph (5 mph).
It's about one-and-three-fifths times as heavy as a Car.
In other words, 66 firkins is 1.6310 times the weight of a Car, and the weight of a Car is 0.61310 times that amount.(for 2009 Ford Taurus; automatic transmission; curb weight)
A 2009 Ford Taurus weighs 40.470 firkins. The first mass-produced car, the Curved Dash Oldsmobile — introduced in 1901 — weighed just 9.4550 firkins.
It's about half as heavy as an Elephant.
In other words, 66 firkins is 0.450 times the weight of an Elephant, and the weight of an Elephant is 2.20 times that amount.(for African bush elephant, Loxodonta africana) (Adult, bull)
A bull African bush elephant weighs about 150 firkins. Among African elephants, both males and females have tusks (whereas female Asian elephants, Elephas maximus, do not have tusks) which can grow to 3 m (10 ft) and weigh up to 2.20 firkins.
It's about two-fifths as heavy as a Tyrannosaurus rex.
In other words, 66 firkins is 0.420 times the weight of a Tyrannosaurus rex, and the weight of a Tyrannosaurus rex is 2.40 times that amount.(for FMNH PR2081, a.k.a. "Sue") (a.k.a. Tyrannosaurus, a.k.a. T-Rex) (estimated live weight)
The notable Tyrannosaurus specimen housed at the Field Museum of Natural History in Chicago, Illinois, "Sue," is estimated to have weighed about 160 firkins while alive. A renowned predator in popular culture, the teeth of tyrannosaurus rex were up to 33.02 cm (13 in) long.