Fechner's double sound pendulum for testing aural discrimination
1898-1908
1898-1908
1850-1900
c.1963
1871-1900
1920-1939
1892
1876
1871-1900
1871-1900
1901-1910
1900-1920
1900
1929
1831-1870
1875-1900
1870-1930
1870
1801-1900
1875-1900
1913
1926
1850-1930
1875-1900
1900-1980
1889
1909
circa 1892
1923