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.
Annuity (European)
"Commutation tables", aptly so named in 1840 by Augustus De Morgan (see his paper "On the Calculation of Single Life Contingencies," "Assurance Magazine", xii. 328), show the proportion in which a benefit due at one age ought to be changed, so as to retain the same value and be due at another age. The earliest known specimen of a commutation table is contained in William Dale's "Introduction to the Study of the Doctrine of Annuities", published in 1772. A full account of this work is given by F. Hendriks in the second number of the "Assurance Magazine", pp. 15–17. William Morgan's "Treatise on Assurances", 1779, also contains a commutation table. Morgan gives the table as furnishing a convenient means of checking the correctness of the values of annuities found by the ordinary process. It may be assumed that he was aware that the table might be used for the direct calculation of annuities; but he appears to have been ignorant of its other uses.