Robert Wood was a professor at Johns Hopkins University during the first half of the 20th century, distinguished for his work on physical optics and also for his sense of humor and his love of mischievous tricks.
In September 1917, Wood and some colleagues embarked for Europe aboard the steamship Adriatic, to help US allies use science in fighting World War I. To hinder German submarines from intercepting the ship, it location was kept secret from everybody, including its passengers.
What follows are Wood's own notes, reproduced in “Doctor Wood" by William Seabrook (1940). The book is out of print, but remains worth reading (if you can find it) for its great store of stories, of which this one is a fair sample.
“We sailed on night after night, the weather growing colder and colder, and the North Star climbing towards the zenith. One afternoon it occurred to Colpitts [one of the traveling scientists] that it was the night of the autumnal equinox, on which both longitude and latitude can be calculated from the elevation of the North Star and the time of sunset [6 hours after noon]. I made a quadrant out of two sticks of wood and a protractor. By sighting one stick on the horizon and the other on the star, I determined its elevation, given which Colpitts, who had timed the sunset, worked out our position in a few minutes. This news spread rapidly, throwing the ship's officers into a frenzy, as all information regarding the course we were sailing was a dead secret. Next morning we discovered the ships' officers had set all of the clocks available to passengers three-quarters of an hour ahead, to confuse and baffle the scientists aboard."
The calculation which enabled Wood and Colpitts to determine the ship's position is described in the lesson plan provided for teachers and accompanying the present web page (http://www.phy6.org/stargaze/Lnavigat.htm).