Although Eisinga was intellectually gifted, he was not allowed to go to school. When he was only 17 years old, he wrote a book about mathematics. When he was 17, he wrote another book about the principles of astronomy. Additional books about special subjects within the field of astronomy followed. Eisinga became a wool carder in Franeker, Netherlands. Through self-education he mastered mathematics and astronomy, which he also studied at the University of Franeker. At the age of 24, he married Pietje Jacobs (? – 24 July 1788) and they had three children, one girl and two boys.