On Sunday, April 2nd, 1911, a 28-year-old maths professor called "Edward de Valera" filled out his census form at home at Morehampton Terrace in Dublin. Across town, Oliver St John Gogarty did the same. In the marital status column he wrote "single", then crossed it out and replaced it with "married", apparently remembering Martha, his wife of five years.
Some entries are missing, of course. They include those for the suffragettes Hanna Sheehy-Skeffington, Anna Haslam and Louie Bennett, all members of the Irish Women's Franchise League, who decided to boycott the census in protest at not having the vote.
When a policeman interrupted one of their meetings on the night before census day to remind them that it was illegal not to fill out the form, the women told him they had arranged for airplanes and submarines to remove them from the soil of Ireland for the night of April 2nd. [Link]