The use of the symbol "π" to represent the ratio of a circle's circumference to its diameter is attributed to Leonhard Euler in the 18th century.
While the publication "Synopsis Palmariorum Matheseos" did exist, its author was William Jones, an English mathematician. He used the symbol "π" in 1706, but it was Euler who popularized its use in the 1730s, and it is widely credited to him.
It's worth noting that the value of pi had been studied and calculated for centuries before the symbol's adoption.