Mendeleev's predicted elements
Dmitri Mendeleev published a periodic table of the chemical elements in 1869 based on properties that appeared with some regularity as he laid out the elements from lightest to heaviest. When Mendeleev proposed his periodic table, he noted gaps in the table and predicted that as-then-unknown elements existed with properties appropriate to fill those gaps. He named them eka-boron, eka-aluminium and eka-silicon with atomic masses 44, 68 and 72 respectively.
C. H. D. Buys Ballot
Buys Ballot devised a tabular method for investigating periodicity in time series. In 1847 he used the table now named after him to determine the period of the sun's rotation from daily observations of temperature in the Netherlands from 1729 to 1846.