A Physicist Remembers traces the effort to measure electron charge, spin, and momentum density on atoms and solids and to compare experiment with theory.Since the complexity of electron arrangements leads to subtle property changes in atoms, molecules and solids, theory and experiment have generally differed by about 1%. The Sagamore conferences have made inroads in reducing this difference. Since 1963 the triennial Sagamore conferences have been held in New York, France, Russia, Finland, Portugal, Germany, Canada, Japan, and England, attracting thousands of participants.Richard J Weiss, original organizer of these conferences, describes the evolution of the X-ray, neutron, and positron probes employed in these measurements. He has performed research with Francis Jenkins at the University of California at Berkeley, Simon Pasternack at Brookhaven National Laboratory, John Slater and B Warren at MIT, Peter Wohlfarth at Imperial College London, M Hart at King’s College London, and Sir N Mott at Cavendish Laboratory.