To give some illustrations of sources of error, I may mention that the earlier observers were convinced that Beulah could not see slight movements of the persons in the room when she was looking fixedly at the ceiling, or that she could not notice the movements of the sister or the mother when she was staring straight into the eyes of the experimenter.
"Psychology and Social Sanity"
Hugo Münsterberg
As in the case of the invention of the steamboat, the public has commonly lightly awarded the credit for each invention to some belated experimenter who, walking more firmly along a road which an earlier pioneer had broken, attained the goal that his predecessor had sought in vain.
"American Merchant Ships and Sailors"
Willis J. Abbot
Five minutes later, Herzog, their servile experimenter, stood bowing and cringing before them.
"The Air Trust"
George Allan England