An tuna da Rasmus Bartholin musamman don ganowa (1669) na sau biyu na hasken haske ta Iceland spar (calcite). Ya wallafa cikakken bayanin abin da ya faru, amma tun da yanayin jiki na haske ba a fahimta ba a lokacin, bai iya bayyana shi ba. Sai bayan da Thomas Young ya gabatar da ka'idar ka'idar haske, c. 1801 cewa bayani ya yiwu. Tambaya: Me yasa Rasmus bai iya bayyana abin ba?
Ba a fahimci yanayin haske ba a lokacin