Hey, I can finally contribute!

I'm curious to find out the history of whisks in use in the western Europe as the only information I can find is hands, a bundle of twigs, and then suddenly the contemporary whisks we know today. Chinese Song Emperor Huizong's Treatise on Tea includes information on early bamboo whisks and proper tea frothing (which was introduced to Japan and eventually adapted to the chasen as we know today).

The earliest instance of meringue in literature I can find is from 1692 by Francois Massialot's Nouvelle Instruction pour les Confitures - Ch XXVIII: Des Meringues & Macarons.

Sabayon/zabaglione is a similar dessert which involves whipping air in to egg yolks. Recipes can be found as early as the late 15th century in Cuoco Napoletano (The Neapolitan Recipe Collection). For this (any many recipes) there's a lot of urban legends about that are hard to trace. It's also difficult to simply parse out culinary history when most of the cookbooks that existed/survived were on meals cooked for the wealthy/royals.

There is also a sugar-based recipe for nougat called natif by Ibn al-Mabrad (Kitab al Tibakhah: A 15th Century Cookbook) which uses beaten egg whites as a thickener when added to a container of cooking fruit syrups, honey, and sugar. If you want to make hulwa or halwa, the recipe instructs to continue beating the egg white / natif mixture when adding toasted almonds, nuts, flour, chickpeas, sesame, etc. In his 10th century cookbook, al-Warraq has an entire chapter for honey-based natif and uses equal parts honey and egg whites. The recipe notes that this requires three hours of beating - said to prevent the eggs from burning. Additional egg whites are added to remove the impurities from the added nuts/flavorings.

Even earlier in 10th century Baghdad, al-Warraq's Annals of the Caliph's Kitchens has a chapter on scrambled eggs and omelettes which require whip eggs for green onion omelette called hirrif and 'ujja maqluba made to resemble furniyya - a type of yeasted cake. It's interesting because a few egg-based recipes throughout the book refer to mixing eggs with your hand.

I've searched other cookbooks written in the 14th and 15th century and can't find anything to bridge the gap between. Western Europe and Mediterranean dessert recipes start to appear around this time in the form of cakes and sweet breads where recipes distinguished between lightly beaten and well beaten eggs. Custards can be referenced in 16th century English cookbooks (A Proper Newe Booke of Cokerye). Some of these recipes that use egg whites in sweets, use it as an icing mixed with rosewater and sugar (adapted from Middle Eastern and South Asian sweets). Platina's On Right Pleasure and Good Health (c. 1470) was translated into French (and Italian and German) in 1505. There is a section on methods on 'le oeufs bien agites a batue' (pp 68-69). Several savoury and sweet tart recipes require beaten egg whites.

The process of making pastry cream is also very similar to Swiss (cooked over a bain-marie) and Italian (cooked simple syrup poured into whipped egg whites) meringues. Pastry creams are typically thickened (e.g. flour, starch, cream, gelatin). Creme anglaise is an exception of this.

So - while the origins are still a bit unclear, the process of whipping eggs and/or albumin was a common technique throughout the world and their ability to suspend air within seems to have been recognized. Gently heating egg whites reduces the time needed to whip them up. Several of these recipes (including the nougats) encourage constant whipping to prevent burning - albeit with tools that were not whisks.