This can be one of the very first signals of the origin of positive thinking.
The US Declaration of Independence, written in 1776, mentions happiness as a right: "We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty, and the pursuit of Happiness."
Religion as the origin of positive thinking
The positive thinking movement and positive psychology derive from the New Thought Movement, at the origin of positive thinking.
This movement took place during the last part of the nineteenth century and the beginning of the twentieth century mainly in North America.
Religious men (thinkers, philosophers, businessmen) started to write about the power of thoughts and positive thinking from a secular point of view.
The writing of several authors surrounds the origin of positive thinking. Their essays, poems and non-fiction writing were focused on the importance of thoughts and the mind: