Julius Lothar Meyer (1830-1895) , a German chemist, worked on classification of the elements. In a paper published in 1870 he presented his discovery of the periodic law, stating that the properties of the elements are periodic functions of their atomic weights.
In Meyer's original periodic table we see the elements arranged in order of atomic weight, but in vertical columns rather than in the rows (or periods) that we are accustomed to. Notice in the diagram shown in this link how Li, Na, K, Rb, Cs appear in the same row.
Read these brief biographical notes on both Meyer and Mendeleev.
Dimitri Ivan Mendeleev (1834-1907), who discovered this same periodic law independently in1869, has received more recognition than Meyer.
Later, Mendeleev explained how he left spaces in his table for as yet undiscovered elements, and predicted properties of those elements.
Mendeleev spoke about The Periodic Law of the Elements at the Faraday Lecture delivered in 1889 and published in the Journal of the Chemical Society.
If you want to know anything about Mendeleev, you probably won't have to look further than this comprehensive Mendeleev site.