The entertainments, the spectacles, were always grand, always pompous, always marvellous, always regal . . . The expense was incredible, the artifice unimaginable, the invention of the nobles.

-Bastiano de'Rossi on the 16th -centur Triumphs staged by Grand Duke Ferdinand of Tuscany.

Dan Bowen, 26, who is building the Samoan float for the inaugural parade, says he might have overdone it. His Samoan float, he figures, is constructed much to well.

It isn't made of cardboard, paper or thin plastic. Bowen, a Falls Church cabinet-maker, used strong wood and stout canvas instead. The grasshut at the stern, floored with hand-made fabric is roofed with cut-up bamboo shades. And of the 29 long floats that Army jeeps will tow past President Carter in the inaugural parade this afternoon, Samoa's is the only one with a built-in hot-air system to keep its riders warm.

Samoa's float, unlike most of the others, is as well built as it looks.

Given half a chance, most float makers will fool you. The gleaming marble dome on the District of Columbia's float isn't really marble, the flowers are plastic, the silver just tinsel and the huge, bewhiskered walrus that will represent Alaska is made of lightweight styrofoam. Modern floats look great when moving, at a distance. But closeup they're, well, chintzy.

It was not always thus.

When the victorious Legions marched through the streets of Rome, they hauled their booty with them. There were piles of gold and jewels on their triumphal chariots.

Cleopatra's barge, you may remember, was a float that floated. "The poop was beaten gold, purple were the sails, and so perfumed that the winds were love-sick with them; the oars were silver, which to the tune of flutes kept stroke . . . She did lie in her pavilion - cloth-of-gold of tissiu - . . . On each side of her stood pretty-dimpled boys, like smiling cupids, with divers-color'd fans."

Cleopatra, as Shakespeare tells us, was a ruler serious about spectacles. And she was not the last.

Mac Fleetwood, who is 40 and a most experienced floatmaker, has been building and unbuilding floats since 1959. Most floats nowadays aren't built by amateurs, or beginners like Dan Bowen, but by professionals like Fleetwood. Yesterday at the Navy yard, in a huge and drafty shed, he was stapling bright blue vinyl to the float that bears the legend "Missouri - Gateway to a New Tomorrow."

Fleetwood is based in Indianapolis. His firm, Exhibition Decorators, Inc., designed the Minnesota float. It also is building Missouri's. Mississippi's, Kentucky's and the plastic-flowered float that will represent the Territory of Guam. Fleetwood is working on the President's Council on Physical Fitness float, which boasts a trampoline and 70-year-old athlete jogging on a treadmill.

"We only have six guys up here." said Fleetwood, "and we didn't start working until Dec. 14, but we'll get them done."

Fleetwood says the float tradition begins with the Rose Bowl floats of 1926 but actually it's older. In the heyday of the Renaissance, no expense was spared for the greeting of new rulers, for triumphs and parades. When Prince Philip entered Antwerp in 1578, 895 carpenters, 234 painters and 498 other artisans worked on arches and on floats.

Floats, in those days, were designed by the greatest artists. When Louis X11 visited Milan in 1507, his parade of welcome was staged by Leonardo. Its climax was a float on which a figure representing Victory sat upon a seat supported by Fortitude, Prudence and Renown. Palladio, Titian, Rubens and Veronese also designed floats. In those days they were pulled by concealed men or horses.

Where the tradition of the float began is anybody's guess. Figures of the gods, and of the Madonna, still move through on the streets on holy days in India, Mexico and Spain. By the 16th century, most extravagant parades were more allegorical than religious, and that is still the case.

Figures representing the aged, the black, the athlete, the Indian, Mark Twain and Charles Lindbergh - as well as many waving women representing beauty - will participate in today's parade.

"Lucky Lindy" will be played by George Dade, 64, who will wear a white silk scarf and goggles. He will ride in the rear cockpit of the Curtiss "Jenny" which the "Lone Eagle" bought for barnstorming from an Americus, Ga., depot (for $500) in 1923, George Dade found the plane on a Coggon, Iowa, pig farm in 1973. The Lindbergh float will represent the chamber of commerce of Americus, and Sandi Payne, "Miss Americus 1976," will ride in its front cockpit.

Most of the floats will glitter, some will broadcast music, one will really shine. It is the theme float of the whole parade. (it cost $15,000, and it is the only float that's being paid for by the inaugural committee.) A kind of chunky sculpture of the letters USA. it will be covered with plastic mirrors.

When the inaugural is over, the mirrors will be sold, the floats will be disassembled, the flat-bed trailers they ride on will be towed away, and their glittering materials, their plastic and their tinsel, will be salvaged, if that's possible, for the next parade.