found dating from at least the Bronze Age. Pre-European Maori waka (canoes) used one or more hollowed stones, tied with flax ropes, as anchors. Many modern moorings still rely on a large rock as the primary element of their design. However, using pure mass to resist the forces of a storm only works well as a permanent mooring; a large enough rock would be nearly impossible to move to a new location. The ancient Greeks used baskets of stones, large sacks filled with sand, and wooden logs filled with lead. According to Apollonius Rhodius and Stephen of Byzantium, anchors were formed of stone, and Athenaeus states that they were also sometimes made of wood. Such anchors held the vessel merely by their weight and by their friction along the bottom. Fluked anchors Iron was afterwards introduced for the construction of anchors, and an improvement was made by forming them with teeth, or "flukes", to fasten themselves into the bottom. This is the iconic anchor shape most familiar to non-sailors. This form has been used since antiquity. The Roman Nemi ships of the 1st century AD used this form. The Viking Ladby ship (probably 10th century) used a fluked anchor of this type, made entirely of iron. Admiralty anchor The Admiralty Pattern anchor, or simply "Admiralty", also known as a "Fisherman", consists of a central shank with a ring or shackle for attaching the rode (the rope, chain, or cable connecting the ship and the anchor). At the other end of the shank there are two arms, carrying the flukes, while the stock is mounted to the shackle end, at ninety degrees to the arms. When the anchor lands on the bottom, it will generally fall over with the arms parallel to the seabed. As a strain comes onto the rope, the stock will dig into the bottom, canting the anchor until one of the flukes catches and digs into the bottom. The Admiralty Anchor is an entirely independent reinvention of a classical design, as seen in one of the Nemi ship anchors. This basic design remained unchanged for centuries, with the most significant changes being to the overall proportions, and a move from stocks made of wood to iron stocks in the late 1830s and early 1840s. Since one fluke always protrudes up from the set anchor, there is a great tendency of the rode to foul the anchor as