### „The centre of gravity of any parallelogram lies on the straight line joining the middle points of opposite sides.“

— Archimedes, libro On the Equilibrium of Planes

Book 1, Proposition 9.

On the Equilibrium of Planes

— Arquímedes, libro On the Equilibrium of Planes

Book 1, Proposition 13.

On the Equilibrium of Planes

— Archimedes, libro On the Equilibrium of Planes

Book 1, Proposition 9.

On the Equilibrium of Planes

— Archimedes, libro On the Equilibrium of Planes

Book 1, Proposition 14.

On the Equilibrium of Planes

— Archimedes, libro On the Equilibrium of Planes

Book 1, Proposition 4.

On the Equilibrium of Planes

— Archimedes, libro The Method of Mechanical Theorems

Proposition presumed from previous work.

The Method of Mechanical Theorems

— Archimedes, libro The Method of Mechanical Theorems

Proposition 6.

The Method of Mechanical Theorems

— Aristarchus of Samos ancient Greek astronomer and mathematician

p, 125

On the Sizes and Distances of the Sun and the Moon (c. 250 BC)

— Archimedes, libro The Method of Mechanical Theorems

of the portion adjacent to the base

Proposition presumed from previous work.

The Method of Mechanical Theorems

— Archimedes, libro On the Equilibrium of Planes

Book 1, Proposition 10.

On the Equilibrium of Planes

— Thomas Little Heath British civil servant and academic 1861 - 1940

this implies the use of similar triangles in the way that the Egyptians had used them in the construction of pyramids

Achimedes (1920)

— Johannes Kepler, libro Astronomia nova

As quoted by Bryant, ibid.

Astronomia nova (1609)

— Mark Twain American author and humorist 1835 - 1910

Quoting a schoolchild in "English as She Is Taught"

— Arthur Schopenhauer, libro Parerga y paralipómena

Vol. 2 "Further Psychological Observations" as translated in Essays and Aphorisms (1970), as translated by R. J. Hollingdale

Parerga and Paralipomena (1851), Counsels and Maxims

— Howard P. Robertson American mathematician and physicist 1903 - 1961

Geometry as a Branch of Physics (1949)

— Immanuel Kant German philosopher 1724 - 1804

Section III On The Principles Of The Form Of The Sensible World

And walk straight down the middle of it.“

— Kate Bush British recording artist; singer, songwriter, musician and record producer 1958

Song lyrics, The Sensual World (1989)

— Morris Kline American mathematician 1908 - 1992

Fuente: Mathematical Thought from Ancient to Modern Times (1972), p. 175

Contexto: To avoid any assertion about the infinitude of the straight line, Euclid says a line segment (he uses the word "line" in this sense) can be extended as far as necessary. Unwillingness to involve the infinitely large is seen also in Euclid's statement of the parallel axiom. Instead of considering two lines that extend to infinity and giving a direct condition or assumption under which parallel lines might exist, his parallel axiom gives a condition under which two lines will meet at some finite point.

— Yahia Lababidi 1973

Signposts to Elsewhere (2008)

— Hans Freudenthal Dutch mathematician 1905 - 1990

Fuente: Mathematics as an Educational Task (1973), p. 363

— Madeleine L'Engle American writer 1918 - 2007

Fuente: A Wrinkle in Time: With Related Readings