Still quite reasonable advice, really.
WWII propaganda - nothing if not subtle.
The cold bit through the thick soles of my riding boots. It crept up my body until I felt miserably frozen in my short jacket. I had snuggled up close to a fir tree… At the main door of the test stand, von Braun, very cold, was standing first on one leg and then on the other. He was holding a rod twelve feet long with a mug of petrol fastened to the end… von Braun lit his gigantic match and held the flame under the exhaust…
There was a swoosh, a hiss, and — crash!
Clouds of smoke rose… Cables, boards, metal sheeting, fragments of steel and aluminum flew whistling through the air… In the suddenly darkened pit of the testing room a milky, slimy mixture of alcohol and oxygen burned spasmodically with flames of different shapes and sizes, occasionally crackling and detonating like fireworks. Steam hissed. Cables were on fire in a hundred places. Thick, black, stinking fumes of burning rubber filled the air. Von Braun and I stared at each other. We were uninjured. The test stand had been wrecked.
Walter Dornberger describes the very first combustion test of a liquid-powered rocket motor.