A page from a 1702 German publication with the title "Reimb Dich, Oder Ich Liß Dich, Das ist: Allerley Materien, Discurs, Concept, und Predigen, welche bißhero in underschiedlichen Tractätlein gedruckt worden" (vd18 10307974). The author explains on this page, and on pages before and after the Holy Trinity. Part of the detailed explanation if a human heart, made of a V (in German printing a "U") and a three as a cap. In the text, the "V" stands for the Latin "unum" (meaning: one, as in: together as one) and the number 3 is of course the Holy Trinity.