What is the largest species of pitcher plant by volume?

What is the largest species of pitcher plant by volume? Nepenthes rajah is widely recognized for producing the largest pitcher traps by volume.

Nepenthes rajah is a giant tropical pitcher plant endemic to Mount Kinabalu and nearby areas of Sabah, on the island of Borneo. Its pitchers are modified leaves that form deep containers filled with digestive fluid. Insects and other animals may slip on the waxy inner surface and fall into the liquid, where enzymes help break down their bodies.

The species is especially famous for enormous lower pitchers, which can reach roughly 41 centimeters in height and hold around 3.5 liters of fluid. Their size allows them to trap more than the small insects associated with many carnivorous plants; larger prey and animal droppings can contribute nutrients in the nutrient-poor mountain soils where the plant grows.

Several other Nepenthes species are serious contenders for size. Nepenthes attenboroughii and Nepenthes truncata can also produce very large pitchers, and individual measurements vary with age and growing conditions. However, when the question specifies overall pitcher volume and asks for the standard single species answer, Nepenthes rajah is the accepted choice.