In 1959 Herbert Bayer designed his Fonetik Alfabet as a proposed simplification of the existing Roman alphabet. This system of writing sought to eliminate the endless variables found in written language and assign one sound to one letter. Within this system, double letter and triple letter sounds were also simplified using ligatures, as illustrated below. 

Even ancient Egyptians sought to simplify common combinations of symbols in Hieroglyphic ligatures. There are hundreds of examples of this type of pictographic shorthand. Below is just one example of this type of Picto-ligature.

The crowns of Upper and Lower Egypt each represent their respective kingdoms. The combined crown represents a united Egypt. Ligature FAQs is a web page that offers a concise description of Ligatures. The latest (quasi) ligature to be forced onto the world is the Euro, the symbol for the United European currency. Will Harris gives his Ligature Schmigature arguments against the need for any ligature in the English language. Many specific visual examples are given for a clear explanation about the general aesthetics of ligatures.